Gang Cao

Office Hours: Tuesday 3:00 - 5:00 p.m. in DUAN F519 •

Research Interests:

It is widely recognized that whoever controls materials controls technology. 

Our research has focused on the discovery, synthesis, and study of novel quantum materials. It encompasses a methodical search for new quantum materials and a systematic effort to elucidate and control novel quantum states in these materials.  We are particularly interested in strongly correlated materials with strong spin-orbit interactions, such as 4d- and 5d-transition metal oxides. Our studies of these oxides over the last three decades have helped initiate and shape novel lines of research on 4d-electron-based ruthenates and 5d-electron-based iridates. These materials now underpin one of the most important and exciting research areas in contemporary condensed matter physics.  Our laboratory is equipped with advanced techniques for materials synthesis and a large suite of experiemental tools for studies of structural and physical properties, often at extreme conditions, i.e., ultralow temperatures, high magnetic fields and high pressures. We have also established broad collaborations with leading scientists in the US and around the world. 

Visit our Group Website and Google Scholar for more information.

Selected Publications:

• Interaction of magnetic fields with spinons in a fractionalized state, Yu Zhang, Hengdi Zhao, Tristan R. Cao, Rahul Nandkishore, Pedro Schlottmann, Lance E. DeLong and Gang Cao, npj Quantum Materials 10, 86 (2025); https://doi.org/10.1038/s41535-025-00809-9
• Time-hidden magnetic order in a multi-orbital Mott insulator.  Wei Li, Iliya Esin, Youngjoon Han, Yincheng Liu, Hengdi Zhao, Honglie Ning, Cora Barrett, Jun-Yi Shan, Kyle Seyler, Gang Cao, Gil Refael, David Hsieh. Nat. Phys. (2025). https://doi.org/10.1038/s41567-024-02752-1
• Transition between heavy-fermion-strange-metal and spin liquid in a 4d-electron trimer lattice, Hengdi Zhao, Yu Zhang, Pedro Schlottmann, Rahul Nandkishore, Lance DeLong and Gang Cao, Phys. Rev. Lett. 132, 226503 (2024); Editors’ Suggestion. https://doi.org/10.1103/PhysRevLett.132.226503   
• Current-sensitive Hall effect in a chiral-orbital-current state, Yu Zhang, Yifei Ni, Pedro Schlottmann, Rahul Nandkishore, Lance E. DeLong, and Gang Cao, Nature Communications 15, 3579 (2024). https://doi.org/10.1038/s41467-024-47823-2    
• Evidence for bootstrap percolation dynamics in a photoinduced phase transition, Tyler Carbin, Xinshu Zhang, Adrian B. Culver, Hengdi Zhao, Alfred Zong, Rishi Acharya, Cecilia J. Abbamonte, Rahul Roy, Gang Cao, and Anshul Kogar, Phys. Rev. Lett. 130, 186902 (2023)
• Control of chiral orbital currents in a colossal magnetoresistance material, Yu Zhang, Yifei Ni, Hengdi Zhao, Sami Hakani, Feng Ye, Lance DeLong, Itamar Kimchi and Gang Cao, Nature 611, 467–472 (2022)
• Emergence of spinons in layered trimer iridate Ba₄Ir₃O₁₀,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, Phys. Rev. Lett.129, 207201 (2022)
• Keldysh space control of charge dynamics in a strongly driven Mott insulator, Xinwei Li, Honglie Ning, Omar Mehio, Hengdi Zhao, Min-Cheol Lee, Kyungwan Kim, Fumihiko Nakamura, Yoshiteru Maeno, Gang Cao, and David Hsieh, Phys. Rev. Lett. 128, 187402 (2022)
• Mechanical control of physical properties in the van der Waals ferromagnet Cr₂Ge₂Te₆ via application of electric current, Hengdi Zhao, Yifei Ni, Bing Hu, Sabastian Selter, Saicharan Aswartham, Yu Zhang, Bernd Buchner, Pedro Schlottmann, and Gang Cao, Phys. Rev. B 106, L041103 (2022)
• Magnetic structure and spin fluctuations in the colossal magnetoresistance ferrimagnet Mn₃Si₂Te₆, Feng Ye, Masaaki Matsuda, Zachary Morgan, Todd Sherline,Yifei Ni, Hengdi Zhao ,and G. Cao, Letter of Phys. Rev. B 106, L180402 (2022); Editors' Suggestion
• Monograph: Physics of Spin-Orbit-Coupled Oxides,  Gang Cao and Lance E. DeLong, Oxford University Press, ISBN 978-0-19-960202-5; 2021
• Colossal magnetoresistance via avoiding fully polarized magnetization in ferrimagnetic insulator Mn₃Si₂Te₆, Yifei Ni, Hengdi Zhao, Yu Zhang, Bing Hu, Itamar Kimchi and Gang Cao, Phys. Rev. B 103, L161105 (2021);Editors' Suggestion
• Flexible lattice in Ca₃Ru₂O₇: Control of the electrical transport via anisotropic magnetostriction, Hengdi Zhao, Hao Zheng, Jasminka Terzic, Wenhai Song, Yifei Ni, Yu Zhang, Pedro Schlottmann and Gang Cao, Phys. Rev. B 104, L121119 (2021)
• The ground state in a proximity to a possible Kitaev spin liquid: An undistorted honeycomb iridate NaxIrO₃ (0.60 < x < 0.80), Hengdi Zhao, Bing Hu, Feng Ye, Minhyea Lee, Pedro Schlottmann and Gang Cao, Letter of Phys. Rev. B 104, L041108 (2021); Editors' Suggestion
• Quest for quantum states via field-editing technology, Gang Cao, Hengdi Zhao, Bing Hu, Nicholas Pellatz, Dmitry Reznik, Pedro Schlottmann and Itamar Kimchi, npj Quantum Mater. 5, 83 (2020)
• Quantum liquid from strange frustration in the trimer magnet Ba₄Ir₃O₁₀, 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 Mater. 5, 26 (2020)
• Topical Review: Towards electrical-current control of quantum states in spin-orbit-coupled matter, Gang Cao, Journal of Physics: Condensed Matter 32, 423001 (2020)  
• Possible quantum paramagnetism in compressed Sr₂IrO₄, D. Haskel, G. Fabbris, J. H. Kim, L. S. I. Veiga, J. R. L. Mardegan, C. A. Escanhoela, Jr., S. Chikara, V. Struzhkin, T. Senthil, B. J. Kim, G. Cao, and J.W. Kim, Phys. Rev. Lett. 124, 067201 (2020)
• Pseudospin-lattice coupling and electric control of the square-lattice iridate Sr₂IrO₄, Feng Ye, Christina Hoffmann, Wei Tian, Hao Zheng, Hengdi Zhao, and G. Cao, Phys. Rev. B 102, 115120 (2020)
• Persistent insulating state at megabar pressures in strongly spin-orbit-coupled Sr₂IrO₄, 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, Phys. Rev. B 101, 144102 (2020)
• Direct detection of dimer orbitals in Ba₅AlIr₂O₁₁, Y. Wang, Ruitang Wang, Jungho Kim, M. H. Upton, D. Casa, T. Gog, G. Cao, J. P. Hill, G. Kotliar,M. P. M. Dean,and X. Liu, Phys. Rev. Lett.,122, 106401 (2019)
• Nonequilibrium orbital transitions via applied electrical current in calcium ruthenate, Hengdi Zhao, Bing Hu, Feng Ye, Christina Hoffmann, Itamar Kimchi and Gang Cao; Phys. Rev. B 100, 241104(R) (2019)
• Electrical control of structural and physical properties via spin-orbit interactions in Sr₂IrO₄, G. Cao, J. Terzic, H. D. Zhao, H. Zheng, Peter Riseborough, L. E. DeLong, Phys. Rev. Lett. 120, 017201 (2018); Editors' Suggestion
• Observation of a pressure-induced transition from interlayer ferromagnetism to intralayer antiferromagnetism in Sr₄Ru₃O₁₀, H . Zheng, W.H. Song, J. Terzic, H. D. Zhao, Y. Zhang, Y. F. Ni, L. E. DeLong, P. Schlottmann and G. Cao, Phys. Rev. B 98, 064418 (2018); Editors' Suggestion
• The Challenge of spin-orbit-tuned ground states in iridates: A Key Issues Review, Gang Cao and Pedro Schlottmann, Reports on Progress in Physics 81 042502 (2018)
• “Novel magnetism of Ir⁵⁺ (5d⁴) ions in the double perovskite Sr₂YIrO₆, G. Cao, T. F. Qi, L. Li, J. Terzic, S. J. Yuan, L. E. DeLong, G. Murthy and R. K. Kaul, Phys. Rev. Lett. 112, 056402 (2014)
• Lattice-tuned magnetism of Ru⁴⁺(4d⁴) ions in single-crystals of the layered honeycomb ruthenates: Li₂RuO₃ and Na₂RuO₃, J. C. Wang, J. Terzic, T. F. Qi, Feng Ye, S. J. Yuan, S. Aswartham, S. V. Streltsov, D. I. Khomskii, R. K. Kaul and G. Cao, Phys. Rev. B 90 161110 (R) (2014)
• Monograph: Frontiers of 4d- and 5d-Transition Metal Oxides, Gang Cao and Lance E. De Long, World Scientific, London, 2013; ISBN: 978-981-4374-859
• Negative volume thermal expansion via orbital and magnetic orders in single-crystal Ca₂Ru_1-xCr_xO₄, T.F. Qi, O.B. Korneta, S. Parkin, L.E. DeLong, P. Schlottmann and G. Cao, Phys. Rev. Lett.105, 177203 (2010)
• Observation of strong spin valve effect in bulk Ca₃(Ru_1-xCr_x)₂O₇, G. Cao, V. Durairaj S. Chikara L. E. DeLong and P. Schlottmann, Phys. Rev. Lett. 100, 159902 (2008)
• Colossal magnetoresistance by avoiding a ferromagnetic state in Mott system Ca₃Ru₂O₇, X. N. Lin, Z.X. Zhou, V. Durairaj, P. Schlottmenn and G. Cao, Phys. Rev. Lett. 95, 017203 (2005)
• Anomalous magnetic and transport properties in magnetic insulator Sr₃Ir₂O₇, G. Cao, Y. Xin, C. S. Alexander, J.E. Crow and P. Schlottmann, Phys. Rev. B66, 214412 (2002)
• Charge density wave formation accompanying ferromagnetic ordering in quasi-one-dimensional BaIrO₃, G. Cao, J.E. Crow, R.P. Guertin, P. Henning, C.C. Homes, M. Strongin, D.N. Basov, and E. Lochner, Solid State Comm.113, 657 (2000)
• Weak ferromagnetism, metal-to-nonmetal transition and negative differential resistivity in single crystal Sr₂IrO₄, G. Cao, J. Bolivar, S. McCall, J.E. Crow, and R.P. Guertin, Phys. Rev. B57, R11039 (1998)
• Observation of a metallic antiferroamgnetic phase and metal-nonmetal transition in Ca₃Ru₂O₇, G. Cao, S. McCall, J.E. Crow and R.P. Guertin, Phys. Rev. Lett. 78, 1751 (1997)
• Thermal, magnetic and transport properties of single crystal Sr_1-xCa_xRuO₃ (0 < x < 1.0), G. Cao, S. McCall, M. Shepard, J. E. Crow, and R. P. Guertin, Phys. Rev. B 56, 321 (1997)
• Magnetic and transport properties of single crystal Ca₂RuO₄: Relationship to superconducting Sr₂RuO₄, G. Cao, S. McCall, M. Shepard, J.E. Crow and R.P. Guertin, Phys. Rev. B 56, R2916 (1997)