Nanoscience

Micromechanical membranes can be quiet frequency sensors even at high amplitude

Cindy Regal — Sat, 21 Mar 2026 18:09:09 +0000

Micromechanical membranes can be quiet frequency sensors even at high amplitude Cindy Regal Sat, 03/21/2026 - 12:09

In our work published in NanoLetters, we develop an experimentally straightforward method to evade this tradeoff. Using a patterned, trampoline-shaped membrane, we find that dual-mechanical-mode operation can bring these sensors to a thermally-limited frequency stability. By measuring and correcting for frequency noise arising at high amplitude, we maintain this high stability when operating beyond the linear regime, opening new opportunities for membrane frequency sensing.

Drum-like membrane resonators are intriguing for precision sensing because their resonance frequencies can be sensitive to a variety of parameters of interest, from mass to thermal radiation. The quest for improved sensitivity in tensioned membranes faces a tradeoff in which a high amplitude of mechanical motion improves signal-to-noise, but too high of a drive (beyond the so-called critical amplitude) introduces nonlinear effects.

In our work published in NanoLetters, we develop an experimentally straightforward method to evade this tradeoff. Using a patterned, trampoline-shaped membrane, we find that dual-mechanical-mode operation can bring these sensors to a thermally-limited frequency stability. By measuring and correcting for frequency noise arising at high amplitude, we maintain this high stability when operating beyond the linear regime, opening new opportunities for membrane frequency sensing.

Off

Traditional

White

New 'vacuum ultraviolet' laser may improve nanotechnology, power nuclear clocks

Steven Burrows — Mon, 16 Mar 2026 17:52:31 +0000

New 'vacuum ultraviolet' laser may improve nanotechnology, power nuclear clocks Steven Burrows Mon, 03/16/2026 - 11:52

Daniel Strain / ��Ҵ�ý�ƽ�� Strategic Communications

Physicists at ��Ҵ�ý�ƽ�� have demonstrated a new kind of vacuum ultraviolet laser that could one day allow scientists to observe phenomena currently out of reach for the most powerful microscopes.

The new laser could allow researchers to follow fuel molecules in real time as they undergo combustion, spot incredibly small defects in nanoelectronics, track time with unprecedented precision and more.

The JILA team will present its preliminary findings on March 17 and March 19 at the American Physical Society Global Physics Summit in Denver.

Off

Traditional

White

Resonant Frequencies: Playing the Edge of Light with a 3-micron Baton

Steven Burrows — Mon, 03 Nov 2025 18:28:05 +0000

Resonant Frequencies: Playing the Edge of Light with a 3-micron Baton Steven Burrows Mon, 11/03/2025 - 11:28

Kenna Hughes-Castleberry / JILA Science Communicator

An ultrastable, scalable and repeatable method for generating soft X-ray beams using a custom-built 3-micron ultrafast laser that is focused into an anti-resonant hollow-core fiber. Image credit: Steven Burrows / JILA

Producing coherent (or laser like) soft X-ray beams in a lab-scale setup represents a many decades-long challenge. Scientists in physics, chemistry, and materials science can use soft X-ray light to study the nanoscale properties of materials and biological systems, to capture behaviors that cannot be seen using visible or even ultraviolet light. But here’s the catch: soft X-rays are notoriously hard to make. To get them, most researchers must travel to large, government-funded synchrotrons—billion-dollar machines, that have limited access and stability. These trips are often rushed, competitive, and only available a few times a year.

Now, a team led by JILA Fellows and ��Ҵ�ý�ƽ�� professors Margaret Murnane and Henry Kapteyn has made a significant advance to make soft X-rays more accessible: with their research group, they have developed an ultrastable, scalable and repeatable method for generating soft X-ray beams using a custom-built 3-micron ultrafast laser that is focused into an anti-resonant hollow-core fiber. This breakthrough, detailed in a paper recently published in APL Photonics, builds on well over a decade of laser development. It presents a technological and experimental advance in high-harmonic generation (HHG), the nonlinear optical process by which high-frequency light is created from lower-frequency driving lasers. The team’s past breakthroughs had shown that the key to generating bright coherent soft X-ray beams was to use mid-infrared (2 – 4 µm) driving lasers focused into a waveguide filled with high-pressure gas. However, no good robust drive lasers existed. In this new breakthrough, the team made giant leaps in transitioning the technique from a heroic optics experiment towards a reliable, applications-oriented light source.

“We wanted to make a coherent X-ray source that doesn’t require a team of optics experts to babysit—something that could find applications in labs across various scientific disciplines and industries,” says JILA research associate Drew Morrill, one of the lead scientists on the project and the paper’s co-first author.
Drew and the team have made a huge step forward by creating bright, ultrastable, coherent soft X-ray beams. In the future, they can enable higher-resolution microscopes that can work in a stroboscopic mode—for example, by capturing nanoscale processes in nanoelectronic, quantum, energy and biological systems, making it possible to understand and optimize them.

A Decade in the Making

Developing JILA’s compact soft X-ray source took over ten years of effort—refining a homebuilt 3-micron wavelength ultrafast laser system when no commercial options existed. From the beginning, the goal was ambitious: to build a mid-infrared laser that was not only powerful and ultrafast but stable enough to operate for entire days without interruption.

To reach that level of performance, the team had to learn how to build fiber lasers from the ground up. That meant mastering delicate tasks like fiber splicing, amplifier construction, and dispersion balancing—adapting technologies initially designed for telecommunications into a new realm of nonlinear fiber optic to seed high power lasers.

One key laser advance came during the early months of the COVID-19 pandemic when the team collaborated with ��Ҵ�ý�ƽ�� Engineering and Physics Professor Scott Diddams. “Scott’s group gave us a roadmap—parts lists, layout guidance, and design principles,” says JILA research scientist Michaël Hemmer, one of the paper’s lead authors. “Then we built it ourselves. The pulses provided by this front-end are outstandingly stable and really the cornerstone of the laser system. These pulses are then amplified using a home-built ytterbium-doped crystal amplifier, providing the high energy needed for HHG while maintaining a clean, controlled beam.”

“The cryogenic ytterbium amplifier is also a second key building block of the system, but it can only run reliably because the front-end is exceptionally reliable; otherwise, it would destroy itself all the time,” notes Hemmer.

Another key contributor was European physicist Dr. Gunnar Arisholm, who shared advanced simulation code that helped the team model complex optical interactions in nonlinear crystals.

“It saved us months of trial and error,” says Hemmer. “He helped train Drew to use the code, which was instrumental in getting the final version running.”

And finally, the key advance was to use optimized waveguides for efficiently converting the laser light into coherent soft X-ray beams.

The line of the first three OPA's that amplify the 3-micron beam. The green light is the parasitic second harmonic light of the 1-micron pump, and the red light is the sum frequency of the 1-micron pump and the 1.5-micron signal. Credit: Gabriella “Gabi” Seifert / JILA

Building and Testing a New Instrument

After designing and re-designing the laser system featuring a fiber-laser-seeded optical parametric chirped-pulse amplifier (OPCPA), the team was finally able to deliver 3 µm wavelength laser pulses with exceptional power and stability. To upconvert this laser light into soft X-rays, the laser pulses are guided through an engineered anti-resonant hollow-core fiber (ARHCF) filled with high-pressure noble gas. Working as a “conductor” for the light, the fiber acts as a waveguide and a container for the interaction medium, allowing the laser and the emitted soft X-rays to travel in phase and interfere constructively over large lengths—opening the door to a new regime of compact, high-brightness sources.

“The laser light travels through the fiber, ionizes the gas, and emits harmonics—overtones of light—far above the frequency of the original beam,” explains JILA graduate student and co-first author Will Hettel.

This process, known as high-harmonic generation (HHG), converts mid-infrared laser pulses into coherent soft X-ray light—similar to how plucking a violin string produces overtones from a single note.

To support this process, the team, with the help of JILA instrument maker and co-author James Uhrich, engineered a precision target system with a modular design: a chassis that allows rapid reconfiguration for different gases and geometries, streamlining the experimental workflow.

“We designed a setup where we can swap out fiber cartridges with micron-level precision,” says Hettel. “It stays aligned even under 10 atmospheres of pressure.”

In terms of output, the system generates soft X-ray photons at energies exceeding 280 eV, reaching the carbon K-edge—a crucial spectral region for biological and materials science applications.

From their design, the researchers found that the setup can run at kilohertz-level repetition rates with continuous, stable beam output for several hours or longer with minimal fluctuation. The system is also rather robust, showing no signs of optical damage even after months of operation. This level of durability is essential for research workflows that demand high uptime and minimal maintenance.

“This isn’t a one-off result,” said Hemmer. “We can run it for days. The beam doesn’t drift. The power doesn’t degrade. That makes it incredibly useful for real experiments.”

Simulating a Symphony

While the laser system was being constructed, another crucial component of the project unfolded in parallel: advanced simulations. To better understand and optimize the HHG process, JILA graduate student Ben Shearer helped develop a fast and flexible numerical model.

“Simulations like this normally take days or weeks to run,” Shearer explains. “We created a version that runs in hours or even minutes—without sacrificing too much of the physics.”

His code, based on a parameterized version of the strong-field approximation, allowed the team to virtually test a wide range of laser pulse durations, energies, and gas conditions before trying them in the lab.

“Ben’s work gave us a cheat sheet,” notes Hemmer. “We could avoid dead ends and prioritize ideas that had a real shot at working.”

These simulations also laid the groundwork for future upgrades, such as transitioning from argon to helium to achieve even higher photon energies.

“If you want to go to the absolute highest energy of high harmonic generation, you need to ionize helium,” says JILA graduate student Gabriella “Gabi” Seifert. “We're getting there; it’s just taking it one step at a time.”

Helium’s higher ionization potential allows stronger driving fields without over-ionizing the medium—a key requirement for pushing HHG to higher energy regimes.

A view of the argon gas cell that the laser is beamed through to produce HHG, showing the fifth harmonic (yellow) and seventh harmonic (blue). Credit: Drew Morrill and Grzegorz Golba / JILA

A World of Possibilities

By building a stable, coherent soft X-ray source that fits on a lab bench, the team has opened the door for broader scientific access to a tool that once required massive infrastructure with limited access.

“We’re really just scratching the surface of what this source can enable,” says Morrill. “With this kind of stability and control, we can start to ask questions that were previously only addressable at synchrotron or free-electron laser facilities, and even go beyond what was possible before.”

Potential applications include high-resolution soft X-ray microscopy of carbon-rich biological material—opening up the possibility of live cell imaging without the need to add light-emitting fluorescent molecules or without the need to freeze the sample.

“This spectral regime is well suited for high-resolution biological imaging,” says JILA graduate student Clay Klein
Other uses lie in probing advanced magnetic materials, such as those explored for ultra-low-energy computing or data storage technologies based on electron spin.

“There’s a long history of new light sources unlocking unexpected science,” said Morrill. “We’re excited to see where this one leads.”

This research was published in APL Photonics.

A team led by JILA Fellows and ��Ҵ�ý�ƽ�� professors Margaret Murnane and Henry Kapteyn has made a significant advance to make soft X-rays more accessible: with their research group, they have developed an ultrastable, scalable and repeatable method for generating soft X-ray beams using a custom-built 3-micron ultrafast laser that is focused into an anti-resonant hollow-core fiber.

Off

Traditional

White

Diamonds are Forever—But Not in Nanodevices

Steven Burrows — Thu, 23 Jan 2025 20:05:16 +0000

Diamonds are Forever—But Not in Nanodevices Steven Burrows Thu, 01/23/2025 - 13:05

Kenna Hughes-Castleberry / JILA Science Communicator

A diffractive optic creates two DUV beams, which are focused and interfered on a sample surface (diamond) using a 4f imaging system to generate a microscopic sinusoidal excitation profile. Image credit: Steven Burrows

Ultrawide-bandgap semiconductors—such as diamond—are promising for next-generation electronics due to a larger energy gap between the valence and conduction bands, allowing them to handle higher voltages, operate at higher frequencies, and provide greater efficiency compared to traditional materials like silicon. However, their unique properties make it challenging to probe and understand how charge and heat move on nanometer-to-micron scales. Visible light has a very limited ability to probe nanoscale properties, and moreover, it is not absorbed by diamond, so it cannot be used to launch currents or rapid heating.

Now, researchers at JILA, led by JILA Fellows and University of Colorado physics professors Margaret Murnane and Henry Kapteyn, along with graduate students Emma Nelson, Theodore Culman, Brendan McBennett, and former JILA postdoctoral researchers Albert Beardo and Joshua Knobloch, have developed a novel microscope that makes examining these materials possible on an unprecedented scale. The team’s work, recently published in Physical Review Applied, introduces a tabletop deep-ultraviolet (DUV) laser that can excite and probe nanoscale transport behaviors in materials such as diamond. This microscope uses high-energy DUV laser light to create a nanoscale interference pattern on a material’s surface, heating it in a controlled, periodic pattern. Observing how this pattern fades over time provides insights into the electronic, thermal, and mechanical properties at spatial resolutions as fine as 287 nanometers, well below the wavelength of visible light.

Murnane states that this new probe capability is important for future power electronics, high-frequency communication, and computational devices based on diamond or nitrides rather than silicon. Only by understanding a material's behavior can scientists address the challenge of short lifetimes observed in many nanodevices incorporating ultrawide-bandgap materials.

A Challenge from an Industry Partner

For Nelson and the other JILA researchers, this project began with an unexpected challenge from materials scientists from one of their industry collaborators: 3M.

“3M approached us to study an ultrawide material sample that wasn’t compatible with our existing microscopes,” Nelson says. The team then collaborated with 3M scientists Matthew Frey and Matthew Atkinson to build a microscope that could image transport in this material.

Traditional imaging methods rely on visible light to see the microscopic composition and transport behaviors in semiconductors and other materials, which is effective for studying materials with smaller bandgaps.

However, materials like diamond, often used in electronic components, have a much larger energy gap between their valence and conduction bands—typically exceeding 4 electron volts (eV)—making them transparent to lower-energy visible and infrared light. Higher-energy photons in the ultraviolet (UV) range or beyond are required to interact with and excite electrons in these materials.

Visible-light setups also struggle with spatial resolution, as their longer wavelengths limit theability to probe the nanoscale dimensions relevant to modern devices.

These limitations inspired the team to think outside the box for their imaging setup.

“We brainstormed a new experiment to expand what our lab could study,” says Nelson.

The result was a multi-year effort to develop a compact microscope that uses DUV light to generate nanoscale heat patterns on a material’s surface without altering the material itself.

Diving into the Deep Ultraviolet Regime

To generate the DUV light, the team first started with a laser emitting pulses at an 800-nanometer wavelength. Then, by passing laser light through nonlinear crystals and manipulating its energy, the team converted it step-by-step into shorter and shorter wavelengths, ultimately producing a powerful deep-ultraviolet light source at around 200 nanometers wavelength.

Each step required precise alignment of laser pulses in space and time within the crystals to achieve the desired wavelength efficiently.

“It took a few years to get the experiment working during the pandemic,” says Nelson, describing the trial-and-error process of aligning light through three successive crystals. “But once we had the setup, we could create patterns on a scale never before achieved on a tabletop.”

To produce the periodic pattern, called a transient grating, the researchers split the DUV light into two identical beams using a diffraction grating. These beams were directed onto the material’s surface at slightly different angles, where they overlapped and interfered with each other, forming a precise sinusoidal pattern of alternating high and low energy. This interference pattern acted as a nanoscale “grating,” temporarily heating the material in a controlled way and generating localized energy variations.

This process allowed the team to study how heat, electrons, or mechanical waves—depending on the material—spread and interacted across the nanoscale grating. The periodicity of the grating, which defined the distance between these high-energy peaks, was closely related to the wavelength of the light source, allowing researchers to get shorter periods by using higher energy (and shorter wavelength) light. The periodicity could be tuned by adjusting the angles of the beams, enabling detailed studies of transport phenomena at microscopic scales. For example, in this experiment, the team achieved grating patterns as delicate as 287 nanometers, a record for laser tabletop setups.

Testing the New DUV Microscope

Once the DUV transient grating system was operational, the team focused on validating its accuracy and exploring its capabilities. Their first test involved thin gold films, which served as a benchmark material due to their well-understood properties. The researchers used their system to generate nanoscale heat patterns, launching acoustic waves at the film’s surface. By analyzing the frequency and behavior of these waves, they extracted material properties such as density and elasticity.

To confirm their results, Nelson developed computer models simulating how the gold film would behave under similar conditions. The experimental data matched her predictions closely, providing a strong validation of the system’s precision.

“Seeing the experiment work and align with the models we created was a relief and an exciting milestone,” Nelson says.

Next, the team used their new DUV microscope to look at diamond, a material prized for its exceptional electronic and thermal properties. Previous techniques for studying diamond often required physical alterations, such as adding nanostructures or coatings, which inadvertently changed its properties. The DUV system eliminated this need, enabling the team to study diamond in its pristine state.

Using their new setup, the researchers observed how charge carriers—electrons and holes—diffused across the diamond after being excited by the DUV light. This process revealed new insights into the nanoscale transport dynamics of diamonds, particularly at nanometer scales.

Beyond validating the system and exploring diamond’s properties, the team’s findings shed light on broader questions of nanoscale heat transport. At such small scales, heat doesn’t always behave as predicted by traditional physical models, which assume a smooth, continuous flow. Instead, nanoscale transport can involve ballistic and hydrodynamic effects, where energy carriers like phonons can travel in a straight line without scattering or can spread like water flowing through channels.

As researchers continue to refine these techniques and explore new materials, this advancement could play a crucial role in the development of high-performance power electronics, efficient communication systems, and quantum technologies. In the quest to push the boundaries of modern devices, diamonds may not last forever—but their impact on nanoscience certainly will.

This research was supported by the STROBE Science and Technology Center and 3M.

Researchers at JILA have developed a novel microscope that makes examining ultrawide-bandgap semiconductors possible on an unprecedented scale. The team’s work, recently published in Physical Review Applied, introduces a tabletop deep-ultraviolet (DUV) laser that can excite and probe nanoscale transport behaviors in materials such as diamond. This microscope uses high-energy DUV laser light to create a nanoscale interference pattern on a material’s surface, heating it in a controlled, periodic pattern. Observing how this pattern fades over time provides insights into the electronic, thermal, and mechanical properties at spatial resolutions as fine as 287 nanometers, well below the wavelength of visible light.

Off

Traditional

White

JILA and University of Colorado Boulder Awarded $20 million to Build a new "Quantum Machine Shop"

Steven Burrows — Fri, 21 Jun 2024 19:36:07 +0000

JILA and University of Colorado Boulder Awarded $20 million to Build a new "Quantum Machine Shop" Steven Burrows Fri, 06/21/2024 - 13:36

Kenna Hughes-Castleberry / JILA Science Communicator

From left to right, Aju Jugessur, Juliet Gopinath, Scott Diddams and Cindy Regal, who will lead the realization of a new facility at ��Ҵ�ý�ƽ��, with JILA's collaboration, for making nano devices. Credit: Patrick Campbell/��Ҵ�ý�ƽ��

JILA Fellow and University of Colorado Boulder physics professor Cindy Regal remarked, "The NQN will be a unique facility for quantum discoveries and technology. I look forward to seeing the NQN as a national resource in quantum and interfacing with a wide range of JILA research.”

Read the full article about the NQN at this link published by ��Ҵ�ý�ƽ�� Today.

On June 20, 2024, the U.S. National Science Foundation awarded JILA and the University of Colorado Boulder a $20 million grant to create the National Quantum Nanofab (NQN), a cutting-edge facility poised to revolutionize quantum technology.

JILA Fellow and University of Colorado Boulder physics professor Cindy Regal remarked, "The NQN will be a unique facility for quantum discoveries and technology. I look forward to seeing the NQN as a national resource in quantum and interfacing with a wide range of JILA research.”

Off

Traditional

White

JILA Graduate Student Nick Jenkins Wins Prestigious Nick Cobb Memorial Scholarship

Steven Burrows — Thu, 14 Dec 2023 18:56:47 +0000

JILA Graduate Student Nick Jenkins Wins Prestigious Nick Cobb Memorial Scholarship Steven Burrows Thu, 12/14/2023 - 11:56

Kenna Hughes-Castleberry / JILA Science Communicator

JILA graduate student Nick Jenkins adjusts a setting on his laser tabletop setup.

Nick Jenkins, a graduate student at JILA, an institute jointly operated by the University of Colorado Boulder and the National Institute of Standards and Technology (NIST), has been awarded the esteemed Nick Cobb Memorial Scholarship. Mentored by JILA Fellows and University of Colorado Boulder professors Margaret Murnane and Henry Kapteyn, Jenkins' research focuses on pioneering tabletop extreme ultraviolet (EUV) microscopy techniques using high-harmonic generation light sources. This innovative work has positioned him as a standout recipient of this significant award.

The Nick Cobb Memorial Scholarship, valued at $10,000, is an annual grant given to an exceptional graduate student studying advanced lithography or a related field. The scholarship, jointly funded by Siemens EDA and SPIE, is more than just financial support. It covers a range of educational expenses, including tuition and fees, textbooks, supplies, and even computer equipment necessary for academic pursuits.

Jenkins' work in EUV microscopy is not just academically excellent but also aligns closely with the technological and innovative spirit of the scholarship. His research under the guidance of Professors Murnane and Kapteyn at JILA is breaking new ground in the field of lithography, contributing to the development of advanced imaging techniques that could revolutionize various technological sectors.

Jenkins' achievement is a testament to his hard work and dedication to his research. It also highlights the supportive and innovative environment at JILA, fostering groundbreaking research in advanced lithography. This scholarship acknowledges Jenkins' accomplishments and supports his future EUV microscopy and lithography endeavors.

Off

Traditional

White

Unlocking the Secrets of Spin with High-Harmonic Probes

Steven Burrows — Fri, 10 Nov 2023 18:01:55 +0000

Unlocking the Secrets of Spin with High-Harmonic Probes Steven Burrows Fri, 11/10/2023 - 11:01

Kenna Hughes-Castleberry / JILA Science Communicator

Tunable ultrafast EUV HHG captures the competing dynamics of spin-flips and spin-transfers in a Heusler Co2MnGa compound. Image credit: Steven Burrows / JILA

Deep within every piece of magnetic material, electrons dance to the invisible tune of quantum mechanics. Their spins, akin to tiny atomic tops, dictate the magnetic behavior of the material they inhabit. This microscopic ballet is the cornerstone of magnetic phenomena, and it's these spins that a team of JILA researchers—headed by JILA Fellows and University of Colorado Boulder physics professors Margaret Murnane and Henry Kapteyn—has learned to control with remarkable precision, potentially redefining the future of electronics and data storage.

As reported in a new Science Advances paper, the JILA team and collaborators from universities in Sweden, Greece, and Germany probed the spin dynamics within a special material known as a Heusler compound: a mixture of metals that behaves like a single magnetic material. For this study, the researchers utilized a compound of cobalt, manganese, and gallium, which behaved as a conductor for electrons whose spins were aligned upwards and as an insulator for electrons whose spins were aligned downwards.

Using a form of light called extreme ultraviolet high-harmonic generation (EUV HHG) as a probe, the researchers could track the re-orientations of the spins inside the compound after exciting it with a femtosecond laser, which caused the sample to change its magnetic properties. The key to accurately interpreting the spin re-orientations was the ability to tune the color of the EUV HHG probe light.

“In the past, people haven't done this color tuning of HHG,” explained co-first author and JILA graduate student Sinéad Ryan. “Usually, scientists only measured the signal at a few different colors, maybe one or two per magnetic element at most.” In a historic first, the JILA team tuned their EUV light probe across the magnetic resonances of each element within the compound to track the spin changes with a precision down to femtoseconds (a quadrillionth of a second).

“On top of that, we also changed the laser excitation fluence, so we were changing how much power we used to manipulate the spins,” Ryan elaborated, highlighting that that step was also an experimental first for this type of research. By changing the power, the researchers could influence the spin changes within the compound.

Using their novel approach, the researchers collaborated with theorist and co-first author Mohamed Elhanoty of Uppsala University, who visited JILA, to compare theoretical models of spin changes to their experimental data. Their results showed strong correspondence between data and theory. “We felt that we'd set a new standard with the agreement between the theory and the experiment,” added Ryan.

Fine Tuning Light Energy

To dive into the spin dynamics of their Heusler compound, the researchers brought an innovative tool to the table: extreme ultraviolet high-harmonic probes. To produce the probes, the researchers focused 800-nanometer laser light into a tube filled with neon gas, where the laser's electric field pulled the electrons away from their atoms and then pushed them back. When the electrons snapped back, they acted like rubber bands released after being stretched, creating purple bursts of light at a higher frequency (and energy) than the laser that kicked them out. Ryan tuned these bursts to resonate with the energies of the cobalt and the manganese within the sample, measuring element-specific spin dynamics and magnetic behaviors within the material that the team could further manipulate.

A Competition of Spin Effects

In their experiment, the researchers found that by tuning the power of the excitation laser and the color (or the photon energy) of their EUV probe, they could determine which spin effects were dominant at different times within their compound. They compared their measurements to a complex computational model called time-dependent density functional theory (TD-DFT). This model predicts how a cloud of electrons in a material will evolve from moment to moment when exposed to various inputs.

Using the TD-DFT framework, Elhanoty found agreement between the model and the experimental data due to competing spin effects within the Heusler compound: spin flips up or down and spin transfers. The spin flips happen within one element in the sample as the spins shift their orientation from up to down and vice versa. In contrast, spin transfers happen within multiple elements, in this case, cobalt and manganese, as they transfer spins between each other, causing each material to become more or less magnetic as time progresses. “What he [Elhanoty] found in the theory was that the spin flips were quite dominant on early timescales, and then the spin transfers became more dominant,” explained Ryan. “Then, as time progressed, more de-magnetization effects take over, and the sample de-magnetizes.”

Designing More Efficient Materials

Understanding which effects were dominant at which energy levels and times allowed the researchers to understand better how spins could be manipulated to give materials more powerful magnetic and electronic properties.

“There’s this concept of spintronics, which takes the electronics that we currently have, and instead of using only the electron’s charge, we also use the electron’s spin,” elaborated Ryan. “So, spintronics also have a magnetic component. Using spin instead of electronic charge could create devices with less resistance and less thermal heating, making devices faster and more efficient.”

From their work with Elhanoty and their other collaborators, the JILA team gained a deeper insight into spin dynamics within Heusler compounds. Ryan said: “It was really rewarding to see such a good agreement with the theory and experiment when it came from this really close and productive collaboration as well.” The JILA researchers are hopeful to continue this collaboration in studying other compounds to understand better how light can be used to manipulate spin patterns.

As reported in a new Science Advances paper, the JILA team and collaborators from universities in Sweden, Greece, and Germany probed the spin dynamics within a special material known as a Heusler compound: a mixture of metals that behaves like a single magnetic material. For this study, the researchers utilized a compound of cobalt, manganese, and gallium, which behaved as a conductor for electrons whose spins were aligned upwards and as an insulator for electrons whose spins were aligned downwards.

Off

Traditional

White

Diamonds in the Quantum Rough: A Sparkling Breakthrough

Steven Burrows — Fri, 03 Nov 2023 17:12:19 +0000

Diamonds in the Quantum Rough: A Sparkling Breakthrough Steven Burrows Fri, 11/03/2023 - 11:12

Kenna Hughes-Castleberry / JILA Science Communicator

Hybrid integration of a designer nanodiamond with photonic circuits via ring resonators. Image credit: Steven Burrows / JILA

While many JILA Fellows focus on qubits found in nature, such as atoms and ions, JILA Associate Fellow and University of Colorado Boulder Assistant Professor of Physics Shuo Sun is taking a different approach by using “artificial atoms,” or semiconducting nanocrystals with unique electronic properties. By exploiting the atomic dynamics inside fabricated diamond crystals, physicists like Sun can produce a new type of qubit, known as a “solid-state qubit,” or an artificial atom.

Because these artificial atoms do not move, one way to let them talk to each other is to place them inside a photonic circuit. The photons traveling inside the photonic circuit can connect different artificial atoms. Like hot air moving through an air duct to warm a cold room, photons move through the quantum circuit to induce interactions between the artificial atoms. “Having an interface between artificial atoms and photons allows you to achieve precise control of the interactions between two artificial atoms,” explained Sun.

Historically, there have been problems with integrating artificial atoms with photonic circuits. This is because creating the artificial atoms (where atoms are knocked out of a diamond crystal) is a very random process, leading to random placement of the artificial atoms, random number of artificial atoms at each location, and random color each artificial atom emits.

Adding to the issue is the incompatibility between the material that hosts the artificial atoms and the material that hosts the photonic circuit. Despite years of research, scientists have yet to find a suitable material that can be a good host of both, making the integration more difficult.

In a new Nano Letters paper, Sun, his research team, and collaborators from Stanford University proposed a new method that would pave the way to solving these two challenges, enabling a more complicated integrated quantum photonic circuit.

This new technique suggests bigger implications for the future of quantum information science, including a way to scale up the circuits. “We now have a way to integrate multiple artificial atoms on one photonic chip,” explained first author and JILA graduate student Kin Fung Ngan.

Combining Diamonds with Other Materials

Historically, diamond has been a popular choice for hosting artificial atoms, as it’s incredibly pure with a large bandgap, allowing physicists more control over the excitation of the atom inside the crystal.

“Our qubits are embedded into the diamond,” explained Ngan. “The benefit here is that we don't need any additional apparatus to hold them in space.”

However, the downside of using a diamond as a qubit host is that it’s incredibly hard to carve, making it difficult to define photonic circuits on them. It is also difficult to get a large diamond piece, unlike other photonic materials such as silicon nitride, where eight-inch wafers are readily available.

To make a large quantum photonic circuit, the diamond-based artificial atoms must be placed inside a photonic circuit based on a different material, such as silicon nitride. Sun, Ngan, and JILA graduate student Yuan Zhan had to find ways to integrate the two different components residing in different materials. “If the integration was not achieved properly, you may have a weaker coupling between the atom and the photon or a loss of photons during transmission. These effects will generate errors when we use photons to mediate interactions between two artificial atoms,” elaborated Sun.

While previous studies tried to combine the two materials using external junctions, the researchers took a different approach by embedding a nanosized chunk of diamond containing the artificial atom directly inside the silicon nitride circuit. Using an ultraprecise placement method for arranging the nanodiamonds on the chip, the researchers added nanodiamonds containing an artificial atom to the chip, coated the entire chip with a silicon nitride layer, and then fabricated photonic circuits centered around each atom. This process ensures the maximum coupling between the artificial atom and the photonic circuit.

Testing the New Experimental Setup

After embedding the artificial atoms into the silicon nitride circuit, the researchers tested the coupling efficiency by exciting the artificial atoms and measuring the light collected by the photonic circuit. Their tests showed that the light shone brighter when the atom was placed inside an optical cavity, revealing the ability to efficiently couple light from the artificial atom to the photonic circuit.

Besides contributing to better compatibility, the ultraprecise placement technique allowed researchers to align several artificial atoms in a row on the same circuit, showing the flexibility of their process and its capability to host multiple qubits at once. Currently, Ngan, Zhan, and other JILA researchers are working on techniques to make these artificial atoms interact with each other with the help of photons and to entangle two artificial atoms with the help of photons.

A Duality in Design

While this current quantum photonic circuit leverages photons as mediators for interactions between the artificial atoms (or qubits), the photons themselves can also act as separate qubits within the system. “The circuit can indeed work for two purposes,” Sun elaborated. “By embedding artificial atoms inside a photonic quantum circuit, we can use the artificial atoms as sources and memories of single photons, potentially reducing the resource required to build a photonic quantum processor.” The combination of the material compatibility and the duality of the qubits in the system suggests that Sun’s circuit design could have big implications for the future of quantum information, offering an effective way to scale up the integrated quantum photonic systems.

In quantum information science, many particles can act as “bits,” from individual atoms to photons. At JILA, researchers utilize these bits as “qubits,” storing and processing quantum 1s or 0s through a unique system.

While many JILA Fellows focus on qubits found in nature, such as atoms and ions, JILA Associate Fellow and University of Colorado Boulder Assistant Professor of Physics Shuo Sun is taking a different approach by using “artificial atoms,” or semiconducting nanocrystals with unique electronic properties. By exploiting the atomic dynamics inside fabricated diamond crystals, physicists like Sun can produce a new type of qubit, known as a “solid-state qubit,” or an artificial atom.

Off

Traditional

White

Going for Gold: New Advancements in Hot Carrier Science

Steven Burrows — Wed, 16 Aug 2023 17:28:57 +0000

Going for Gold: New Advancements in Hot Carrier Science Steven Burrows Wed, 08/16/2023 - 11:28

Kenna Hughes-Castleberry / JILA Science Communicator

An artistic representation of a "hot carrier" gold nanoparticle. Image credit: Steven Burrows / JILA

In a new ACS Nano paper, JILA and NIST Fellow David Nesbitt, along with former graduate student Jacob Pettine and other collaborators, developed a new method for measuring the dynamics of specific particles known as “hot carriers,” as a function of both time and energy, unveiling detailed information that can be used to improve collection efficiencies.

Within nanoscience, gold nanoparticles have emerged as fascinating building blocks for numerous applications, ranging from catalysis and sensing to biomedicine. Among their remarkable properties is the ability to generate large numbers of “hot carriers” upon light absorption. Hot carriers refer to highly energetic charge carriers, such as electrons, which bounce around inside the gold nanoparticles. If the kinetic energy stored in these hot carriers could be fully collected, it would lead to significant efficiency boosts and new capabilities in photovoltaics, photochemical catalysis, nanophotonics, and nanoelectronics.

Hot carriers can be collected for energy harvesting in several applications, such as solar cells. However, how to achieve technologically useful collection efficiencies in systems incorporating nanoscale metals remains unclear. “Whereas solar cells can exhibit energy collection efficiencies over 30%, many gold nanoparticle studies show less than 1% efficiencies,” explained former JILA graduate student Jacob Pettine, now a Director's Postdoctoral Fellow at Los Alamos National Laboratory. “But, if we can boost these underlying collection efficiencies, then nanoparticles have the added bonus of operating across a broader range of the solar spectrum than silicon. There is room for growth; in some cases, hot electron extraction from these nanoparticles has even exceeded 10%. The challenge is understanding what exactly is happening at these tiny length scales and very fast time scales.”

As Good As Gold: A Study of Metals

Gold has played a significant role in human history, captivating civilizations for centuries due to its inherent beauty, rarity, and versatility. “Gold is an amazing material,” Nesbitt elaborated. “In macroscopically large ‘chunks,’ gold behaves in a way that is essentially chemically inert.” However, at a nanoscale, gold behaves differently. “At the nanoscopic level, ‘small’ clusters of gold (say 10–10,000 atoms) can exhibit exceptionally high chemical reactivity, for example, in developing catalysts for oxidation/reduction of CO (carbon monoxide) to/from CO2,” added Nesbitt. “Of even greater interest, these small gold clusters are extremely good at absorbing visible solar light, with many orders of magnitude higher absorption per unit area than the ‘blackest’ materials like carbon soot. That’s ‘ironic’ for a metal like gold, which we typically think of as highly reflective and not absorbing!”

Thanks to their ability to absorb sunlight, the gold nanoparticles can be filled to the energetic “brim” with hot carriers. Pettine, the study’s lead author, and Nesbitt wanted to study the hot carrier dynamics and needed a method to track the energy decay of these hot carriers throughout their short lifetimes. “When you come in with a photon, and that light gets absorbed inside of these particles, the question becomes, how does the electron’s energy decay after being excited?” Nesbitt stated. “How does this energy spill out? Does it simply instantaneously heat up the gold atoms (which is not terribly useful) or keep the energy in hot electron currents bouncing around inside a gold cluster?” To answer these questions, Pettine and Nesbitt realized they would have to develop a novel procedure to dive deeper into these nanomaterials.

Nanoscale Games of Darts

In their experimental setup, Pettine and Nesbitt combined two laser beams to excite, and then detect, the hot carriers. According to Pettine, “The system we built up in the Nesbitt Lab has allowed us to perform time-resolved studies on single nanoparticles. This is a totally unique capability, which we use with a technique called photoemission spectroscopy to resolve how fast the electrons decay or jump down from a higher to lower energy level, as a function of excitation energy.” Photoemission spectroscopy has a rich historical legacy within physics. “It is based on the photoelectric effect,” Pettine added. “The idea for our study is to kick electrons out of the system, detect them, and reconstruct what they were doing in the nanoparticle.”

To capture and measure the hot carrier dynamics, the researchers first excited their gold nanoparticles with a red laser, transforming them into hot carriers. Then, a blue laser probed the system and ejected the cluster of hot carriers out of the nanoparticles. Using a series of copper plates at various voltages as a lens for these electrons, the researchers could focus them onto a detector. Similar to a game of darts, the electron “splatter” on this detector could then be used to measure their energy dynamics. “The general idea is that you're taking a snapshot of the system,” Pettine elaborated. “The idea is to come in and knock it out of equilibrium with the first pulse, then we come in with a second pulse and see what the electrons are up to. We can do several things with this second pulse, like measure the absorption or reflectivity of the nanoparticle, but in our case, we can use it to kick out electrons so we can see how fast they move and in what direction.”

From their new method, Pettine and Nesbitt found some unexpected results. “Our findings help us shed light on a few more basic ideas,” said Pettine. “Amazingly, we still don't fully understand the dynamics in simple metals like gold when you shine a light on them. In fact, our recent work, including this paper, teaches us a few new things about gold in general. In nanoscale gold, whereas you might expect the surface to play a huge role due to the huge surface-to-volume ratio, we find that it plays almost no role! So, everything we're looking at really comes from the bulk of the material, and by studying these nanoparticles, we can actually get a remarkably accurate view of what likely happens in macroscopic bulk metal, like a chunk of gold.”

In a new ACS Nano paper, JILA and NIST Fellow David Nesbitt, along with former graduate student Jacob Pettine and other collaborators, developed a new method for measuring the dynamics of specific particles known as “hot carriers,” as a function of both time and energy, unveiling detailed information that can be used to improve collection efficiencies.

Off

Traditional

White

How to Bind with Metals and Water: A New Study on EDTA

Steven Burrows — Thu, 27 Jul 2023 17:30:53 +0000

How to Bind with Metals and Water: A New Study on EDTA Steven Burrows Thu, 07/27/2023 - 11:30

Kenna Hughes-Castleberry / JILA Science Communicator

The near-universal ability of EDTA to accommodate metal cations comes from its molecular flexibility, which allows it to respond to the chemical nature of the metal ion it binds. Image credit: Steven Burrows / JILA

Metal ions can be found in almost every environment, including wastewater, chemical waste and electronic recycling waste. Properly recovering and recycling valuable metals from various sources is crucial for sustainable resource management and contributes to environmental cleanup. Because of the scarcity of some of these metals, such as rare earth elements or nickel, scientists are working to find ways to remove these ions from the waste and recycle the metals. One method used to remove these metals is to bind them to other molecules known as chelators or chelating agents. Chelators have multiple molecular groups that combine to form binding sites with a natural affinity for binding metal ions, making them a natural choice to extract metals from toxic waste. Ethylenediaminetetraacetic acid, or EDTA, is a chelator commonly used in metal removal and many other applications, including medicine. “EDTA is used to treat heavy-metal poisoning,” JILA graduate student Lane Terry explained. “So, if you have lead poisoning, you can take EDTA, which binds to the lead and then safely passes through your system. It's also used as a food preservative. So EDTA is everywhere. It's in one of my topical creams, etc.” EDTA is also commonly used in various laboratories, including many within JILA.

To understand how EDTA binds to these metal ions and water molecules, Madison Foreman, a former JILA graduate student in the Weber group, now a postdoctoral researcher at the University of California, Berkeley, Terry, and their supervisor, JILA Fellow J. Mathias Weber, studied the geometry of the EDTA binding site using a unique method that helped to isolate the molecules and their bound ions, allowing for more in-depth analyses of the binding interactions. They published a series of three papers on this topic. In their first paper, published in the Journal of Physical Chemistry A, they found that the size of the metal ion changes where it sits in the EDTA binding site, which affects other binding interactions, especially with water.

Binding to Metal Ions

EDTA is a chemical commonly found in a chemistry or biology laboratory. “EDTA is employed in many different contexts,” explained Weber. “Whenever you want to get rid of a metal ion in a solution, you throw EDTA into the solution. EDTA will bind to pretty much any metal ion across the periodic table. That's what makes it so widely used in chemistry and biochemistry.” Because of this, EDTA as a model system can reveal more about similar binding behaviors in proteins, including some found in the human body. “People are using it as a model for the binding sites of metal ions in proteins,” said Weber.

However, actually observing the mechanics of EDTA binding is rather tricky. “So, to see exactly what’s going on, you must isolate your target complex from other species,” explained Weber. “That's why we bring these ions into the gas phase, where we can control the number of solvent molecules they interact with, first without any solvent, then selectively start adding solvent one molecule at a time to see what changes.” To do this, the EDTA ions were coaxed into a gas phase. “We then cool them in a cryogenic ion trap to about 50 Kelvin,” Foreman added. “After that, we attach weakly bound nitrogen molecules, which act as messengers telling us later that a photon has been absorbed. We only let those [tagged EDTA] molecules into the second half of the experiment. So there's nothing else, and we have only one sort of ion.”

These tagged ion clusters were then bombarded with light from a tunable laser, which helped detect the target clusters. “We hit that nitrogen-tagged EDTA complex with a photon, which ejects the nitrogen tag,” added Foreman. “So now we have these two fragments flying along, the complex ion and the nitrogen, as well as some amount of undissociated cluster that still has the nitrogen on it.” Thanks to this nitrogen eviction, the researchers can detect that light was absorbed. “After this, we do a second mass spectrometry step to distinguish the undissociated parent ions from the fragment ions,” Weber clarified. “We selectively only measure the intensity of those fragment ions as we tune our laser. That’s how we measure a photo-dissociation spectrum which is the analog of the infrared absorption spectrum of that complex.”

The infrared absorption spectrum of these complexes is something physicists and chemists often refer to, but because multiple atoms and molecules tend to contaminate a sample, this spectrum can be hard to isolate. With their gas-phase method, Weber and his team were able to create an analogous process to the infrared absorption measurements and understand more about the molecular behavior of EDTA. “Now, we can analyze the absorption features from that infrared spectrum to tell us something about the molecular structure,” added Weber. “So encoded in this infrared spectrum is how the EDTA molecule interacts with that metal ion, how its functional groups are oriented, and how that orientation changes as you attach water to it or bring it into solution.”

Binding to Water Molecules

As there is usually water around EDTA and proteins, as in the human body, Weber and his team were curious to understand how EDTA’s behavior changes when interacting with water. “These binding sites in proteins bind to metal ions like calcium or magnesium with similar functional groups as those in EDTA,” Weber explained. “And in proteins, the interaction between the metal ion and the protein binding pocket often does not allow lots of water molecules around it. Instead, it allows one or two in the vicinity. So, one could argue that the behavior of EDTA in the gas phase is actually a good model for trying to understand how these binding sites work.”

In one experiment, published in the Journal of Physical Chemistry Letters, the researchers added water to the metal-EDTA complex one molecule at a time to see how small amounts of water affected the EDTA. “Here you start with just the EDTA metal complex, and then you add one water molecule and see where it binds and how it deforms the metal-EDTA complex as a whole,” Weber added. “Then you can add the second water molecule and see how it influences the complex. In our research, we contrasted it with full solvation, full hydration.”

Studying how EDTA binds metals while in the presence of water can also help researchers better understand the binding processes happening within the human body. “One of the main proteins that EDTA is used to emulate is calmodulin, as its binding pockets are kind of similar,” Foreman explained. “Calmodulin is part of a larger class of proteins. They're all over the body serving all sorts of different functions. But the primary function of calmodulin is as a calcium mediator, so it reacts to the presence of calcium and signals other proteins to perform their functions. This can have effects on everything from hormones to muscle contraction.” Because calmodulin usually binds more to calcium than magnesium in water, the researchers wanted to see if EDTA mimicked this behavior in solution. “When we then look at EDTA, in solution, we see a similar trend in binding affinity, [where EDTA] would prefer to bind calcium than magnesium,” stated Foreman. “So then, by looking at it in the gas phase, or with just a few water molecules, we can see that the structure of the EDTA metal complex does change between magnesium and calcium. And that gives us a hint as to why these proteins might be more selective to some ions than others.”

Recycling Metal Ions

Weber and his team first studied how the molecule binds to alkaline earth metals (such as magnesium, calcium, strontium, or barium) to understand EDTA's interaction with different metal ions. In a second paper, published in 2023 in the Journal of Physical Chemistry A, the researchers found geometric differences in bindings between transition metals, like manganese, cobalt, and nickel, and alkaline earth metals, like calcium or magnesium. “The alkaline earth ions are simple ions. They present a spherically symmetric charge distribution to the outside world,” Weber elaborated. “So they're really round. The transition metals we published in the paper, their electronic structure brings directionality to their bonding with other molecules; they do not look like a spherically symmetric charge distribution. I usually phrase this where the alkaline earth metals are round and the transition metals are spiky. Their electronic structure produces “arms” or “spikes” in a structural template that allows other molecules to bind to them in a very structured way.”

Understanding how EDTA binds to various metals can give Weber and other scientists insight into using molecules that are similar to EDTA in wider applications, such as metal recycling. “Imagine nickel, cobalt, or rare earth metals, everything that you need for things from electric vehicles to batteries to your cell phone,” stated Weber. “These metals need to be removed from electronics waste during recycling; then they need to be purified. One way to do that is to grab them with something [like EDTA] …Lane gathered background information on using chelators for rare earth metal recycling. She actually wrote a proposal on that process. And there are other, very different kinds of ion receptors, too.” They’re hopeful that their results can help other scientists and engineers improve current metal chelation applications.

To understand how EDTA binds to metal ions and water molecules, Madison Foreman, a former JILA graduate student in the Weber group, now a postdoctoral researcher at the University of California, Berkeley, Terry, and their supervisor, JILA Fellow J. Mathias Weber, studied the geometry of the EDTA binding site using a unique method that helped to isolate the molecules and their bound ions, allowing for more in-depth analyses of the binding interactions. They published a series of three papers on this topic. In their first paper, published in the Journal of Physical Chemistry A, they found that the size of the metal ion changes where it sits in the EDTA binding site, which affects other binding interactions, especially with water.

Off

Traditional

White