Research

Discovery and Study of Novel Quantum Materials

Our research program encompasses a methodical search for new materials in single-crystal form, and a systematic effort to elucidate the underlying physics of these materials (e.g. ).

This research program has been supported by both NSF and DOE.

Materials Discovery and Synthesis: Wesearch for new, interesting quantum materials and sythesize them in single-crystal form using flux, floating-zone, electrochemical deposition and the newly developed magneto-synthesis techniques (see Section Facilities).

We are particularly interested in high-Z (Z being atomic number) materials with comparable Coulomb and spin-orbit interactions (see Section Quantum Materials).

Field-Tailoring Technology for Magneto-Synthesis:The discovery of novel quantum materials requires innovative synthesis approaches. Wehave been developing a new Field-Tailoring Technology (FTT)that utilizes a laser molten/floating zone furnace coupled with a superconducting magnet to synthesize highly ordered materials that are inaccessible via existing techniques (see proof-of-concept results in &.

Materials Characterization: We utilize a wide suiteof tools for experimental studies of structural, transport, magnetic, thermal and dielectric properties as functions of chemical composition, temperature, magnetic field,pressure and electrical current. Measurements are often carried out at extreme conditions, i.e., ultralow temperatures, high magnetic fields and high pressures (see Section Facilities)

A Common Feature Shared byAll Materials We Are Interested:Quantum states of these materialsare primarilydictated by a combined effect of both spin-orbitandCoulomb interactions andfeaturea high susceptibility to external stimuli, such as magnetic field B, electrical field E, pressure P, light hv or electrical current I.These external stimuli readily couple to the lattice and are control "knobs" we utilize to discover andstudy exotic states, as schematically shown below.

A schematic of the high susceptibility of a quantum statesupported by so and U to external stimuli, such as magnetic field B, electrical field E, pressure P, light hv or electrical current I.
Highlights of Recent Work
I. Chiral orbital currents
  • ,Gang Cao, Hengdi Zhao, Yu Zhang, Alex Fix, Tristan R. Cao, Dhruva Ananth, Yifei Ni,Gabriel Schebel, Rahul Nandkishore, Itamar Kimchi, Hua Chen, Feng Ye and Lance E. DeLong; Physical Review Letters 135, 146504 (2025)
  • ,Tristan R. Cao,Gabriel Schebel, Arabella Quane, Hengdi Zhao, Yu Zhang, Feng Ye, Longji Cui, and Gang Cao, Communications Physics 9, 183(2026)
  • ,Yu Zhang, Yifei Ni, Hengdi Zhao, Sami Hakani, Feng Ye, Lance DeLong, Itamar Kimchiand Gang Cao,Nature611,467–472 (2022)
  • , Yu Zhang, Yifei Ni, Pedro Schlottmann, Rahul Nandkishore, Lance E. DeLong, and Gang Cao, Nature Communications 15, 3579 (2024)
  • , Yifei Ni, Hengdi Zhao, Yu Zhang, Bing Hu, Itamar Kimchi and Gang Cao, Physical Review B103, L161105 (2021)
II. Magneto-synthesis
  • , Gang Cao, Hengdi Zhao, Bing Hu, Nicholas Pellatz, Dmitry Reznik, Pedro Schlottmann and Itamar Kimchi, npj Quantum Materials5, 83 (2020)
  • Tristan R. Cao, Hengdi Zhao, Xudong Huai, Arabella Quane, Varun Narayanan, Thao T. Tran, Feng Ye and Gang Cao, npj Quantum Materials 11, 21 (2026)
III. Emergent quantum states in trimer lattices
  • ,Gang Cao, Hengdi Zhao, Adrienne Bond, Tristan R. Cao, Gabriel Schebel, Arabella Quane, Yifei Ni, Yu Zhang, Logan Wall, Rahul Nandkishore, Pedro Schlottmann, and Feng Ye, Physical Review Letters 137, 036502 (2026); Editors' Suggestion.
  • , Yu Zhang, Hengdi Zhao,Tristan R. Cao, Rahul Nandkishore, Pedro Schlottmann, Lance E. DeLong and Gang Cao, npj Quantum Materials10, 86 (2025);
  • ,Hengdi Zhao, Yu Zhang, Pedro Schlottmann, Rahul Nandkishore Lance E. DeLong, and Gang Cao, Physical Review Letters 132, 226503 (2024)
  • , Yu Zhang, Hengdi Zhao,Tristan R. Cao, Rahul Nandkishore, Pedro Schlottmann, Lance De Long, and Gang Cao, . To appear in npj Quantum Materials (2025)
  • , G. Cao, H. D. Zhao, H. Zheng, Y. F. Ni, Christopher. A. Pocs, Y. Zhang, Feng, Ye,Christina Hoffmann, Xiaoping Wang,Minhyea Lee, Michael Hermele and Itamar Kimchi, npjQuantum Materials. 5, 26 (2020)
  • ,Y. Shen, J. Sears, G. Fabbris, A. Weichselbaum, W. Yin, H. Zhao, D. G. Mazzone, H. Miao, M. H. Upton, D. Casa, R. S. Acevedo-Esteves, C. Nelson, A. M. Barbour, C. Mazzoli, G. Cao, and M. P. M. Dean,Physical Review Letter 129, 207201(2022)
IV. Electrical control of quantum states
  • , G. Cao, J. Terzic, H. D. Zhao, H. Zheng, Peter Riseborough, L. E. DeLong, Physical Review Letter120, 017201 (2018)
  • , Hengdi Zhao, Bing Hu, Feng Ye, Christina Hoffmann, Itamar Kimchiand Gang Cao;Physical Review B100, 241104(R)(2019)
  • , Gang Cao,Journal of Physics: Condensed Matter 32, 423001 (2020)
V. High pressure and magnetostriction studies
  • ,H. Zheng,W.H. Song, J. Terzic, H. D. Zhao, Y. Zhang, Y. F. Ni, L. E. DeLong, P. Schlottmann and G. Cao,Physical Review B98,064418(2018)
  • , Chunhua Chen,Yonghui Zhou,Xuliang Chen, Tao Han,Chao An, Ying Zhou, Yifang Yuan,Bowen Zhang,Shuyang Wang, Ranran Zhang,Lili Zhang, Changjing Zhang, Zhaorong Yang, Lance E. DeLongandGangCao,Physical Review B101, 144102 (2020)
  • , Hengdi Zhao, Hao Zheng, Jasminka Terzic, Wenhai Song, Yifei Ni, Yu Zhang, Pedro Schlottmann, and Gang Cao, Physical Review B 104, L121119 (2021)
VI. Key Issue Review and book on Iridates and ruthenates
  • , Gang Cao and Pedro Schlottmann, Reports on Progress in Physics 81 042502(2018)
  • , Gang Cao and Lance E. De Long, Oxford University Press;Oxford, 2021