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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: We search 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 or Magneto-Synthesis: The discovery of novel quantum materials requires innovative synthesis approaches. We have 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 suite of 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 by All Materials We Are Interested:  Quantum states of these materials are primarily dictated by a combined effect of both spin-orbit and Coulomb interactions and feature a 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 and study exotic states, as schematically shown below.    

Highlights of Recent Work

I. Chiral orbital currents

• , Yu Zhang, Yifei Ni, Hengdi Zhao, Sami Hakani, Feng Ye, Lance DeLong, Itamar Kimchi and Gang Cao, Nature 611, 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 B 103, L161105 (2021)

II. Quantum spin liquids in trimer lattices 

• , 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, , 2024
• , 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,  npj Quantum 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)

III. Electrical control of quantum states

• , G. Cao, J. Terzic, H. D. Zhao, H. Zheng, Peter Riseborough, L. E. DeLong, Physical Review Letter 120, 017201 (2018)
• , Hengdi Zhao, Bing Hu, Feng Ye, Christina Hoffmann, Itamar Kimchi and Gang Cao; Physical Review B 100, 241104(R) (2019)
• , Gang Cao, Journal of Physics: Condensed Matter 32, 423001 (2020) 

IV. Magneto-synthesis

• , Gang Cao, Hengdi Zhao, Bing Hu, Nicholas Pellatz, Dmitry Reznik, Pedro Schlottmann and Itamar Kimchi, npj Quantum Materials 5, 83 (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 B 98, 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. DeLong and Gang Cao, Physical Review B 101, 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