Quantum Materials

Strongly Correlated Materials

Unconventional superconductivity is one of the most intriguing emergent phenomenon out of strongly correlation effect in condensed matter systems. Cuprates, holding the highest critical temperature Tc for superconductivity in ambient pressure, still puzzles physicists for the underlying physics albeit of more than three decades of intensive studies.

The recent discovery of superconductivity in oxygen-reduced monovalent nickelates in 2019 has raised a new platform for the study of unconventional superconductivity, with similarities and differences with cuprates. My recent theoretical studies, combining first-principles density functional theory methods and exact diagonalization for many-body calculations, address the electronic structure and elementary excitations of infinite-layer nickelates. The two-orbital scenario as well as the RIXS spectra for NdNiO2 and LaNiO2 are shown in the Figure below.

Figure: a-c, Electronic structure of the parent compound of infinite-layer nickelates, and Wannier orbitals for the minimal two-orbital model, taken from Ref[1]. d-h, Experimental and calculated RIXS maps of LaNiO2, taken from Ref[1].

Publications:

[1] M Hepting, D Li, CJ Jia*, H Lu, E Paris, Y Tseng, X Feng, M Osada, E Been, Y Hikita, Y-D

Chuang, Z Hussain, KJ Zhou, A Nag, M Garcia-Fernandez, M Rossi, HY Huang, DJ Huang, ZX

Shen, T Schmitt, HY Hwang, B Moritz, J Zaanen, TP Devereaux, WS Lee* (*co-corresponding author),

"Electronic structure of the parent compound of superconducting infinite-layer nickelates",

Nature Materials 19, 381-385 (2020)

[2] Emily Been, Wei-Sheng Lee, Harold Y Hwang, Yi Cui, Jan Zaanen, Thomas Devereaux, Brian

Moritz, Chunjing Jia, "Electronic Structure Trends Across the Rare-Earth Series in Superconducting

Infinite Layer Nickelates", Physical Review X 11, 011050 (2021).

[3] Z. Chen, M. Osada, D. Li, E.M. Been, S.-D. Chen, M. Hashimoto, D. Lu, S.-K. Mo, K. Lee,

B.Y. Wang, F. Rodolakis, J.L. McChesney, C.J. Jia, B. Moritz, T.P. Devereaux, H.Y. Hwang, Z.-

X. Shen, "Electronic structure of superconducting nickelates probed by resonant photoemission

spectroscopy", Matter 5, 1 (2022)

[4] E.M. Been, K.H. Hsu, Y. Hu, B. Moritz, Y. Cui, C.J. Jia, T.P. Devereaux, "On the nature of

valence charge and spin excitations via multi-orbital Hubbard models for infinite-layer nickelates",

Frontiers in Physics, 10, 836959 (2022)

[5] C. Peng, H.-C. Jiang, B. Moritz, T. P. Devereaux, C.J. Jia, "Superconductivity in a minimal

two-band model for infinite-layer nickelates", arXiv:2110.07593.

[6] Bai YangWang, Tiffany CWang, Yu-Te Hsu, Motoki Osada, Kyuho Lee, Chunjing Jia, Caitlin

Duffy, Danfeng Li, Jennifer Fowlie, Malcolm R Beasley, Thomas P Devereaux, Ian R Fisher, Nigel

E Hussey, Harold Y Hwang, "Rare-Earth Control of the Superconducting Upper Critical Field in

Infinite-Layer Nickelates", arXiv:2205.15355.

Low Dimensional Materials

2D materials are a class of materials consisting of single-layer atoms (or few layer

atoms in the broad sense), in which the electrons’ movements are restricted in the third dimension and novel phenomena emerge. Such nontrivial phenomena including nontrivial topology in electronic structure, strong excitonic coupling, charge density wave, quantum spin Hall effect etc, have been observed in various of 2D materials, especially in transition-metal dichalcogenide (TMDC). Emergent phenomena such as superconductivity have also been observed in bi-layer graphene and bi-layer TMDCs with magical twisted angle. My research on 2D materials mainly focused on the study of quantum spin Hall effect in 2D materials WTe2 and MoTe2, and the investigation of the electronic structure for excitonic insulator candidates ZrTe2.

Another important class of low dimensional materials of interest is quantum magnetic materials. Low dimensionality, strong correlations, and geometric frustration can combine to yield exotic states of quantum matter, such as the long sought-after "quantum spin liquid" that still remains elusive.

Electronic topology and Kitaev interactions in triangular, kagome, and pyrochlore lattices in low dimensional materials offer exciting opportunities to access physics not present in traditional materials.

Figure: a-c, ab initio electronic structure of transition-metal dichalcogenide monolayers, taken from Ref[3].

Publications:

[1] Shujie Tang, Chaofan Zhang, Dillon Wong, Zahra Pedramrazi, Hsin-Zon Tsai, Chunjing

Jia, Brian Moritz, Martin Claassen, Hyejin Ryu, Salman Kahn, Juan Jiang, Hao Yan, Makoto

Hashimoto, Donghui Lu, Robert G Moore, Chan-Cuk Hwang, Choongyu Hwang, Zahid Hussain,

Yulin Chen, Miguel M Ugeda, Zhi Liu, Xiaoming Xie, Thomas P Devereaux, Michael F Crommie,

Sung-Kwan Mo, Zhi-Xun Shen, "Quantum spin Hall state in monolayer 1T’-WTe2", Nature Physics

13, 683 (2017)

[2] Shujie Tang, Chaofan Zhang, Chunjing Jia, Hyejin Ryu, Choongyu Hwang, Makoto Hashimoto,

Donghui Lu, Zhi Liu, Thomas P Devereaux, Zhi-Xun Shen, Sung-Kwan Mo, "Electronic structure

of monolayer 1T’-MoTe2 grown by molecular beam epitaxy", APL Materials 6, 026601 (2018)

[3] M. Claassen, C. J. Jia, B. Moritz, T. P. Devereaux, "All-Optical Materials Design of Chiral

Edge Modes in Transition-Metal Dichalcogenides", Nature Communications 7, 13074 (2016)

[4] Yekai Song, Chunjing Jia, Hongyu Xiong, Binbin Wang, Zhicheng Jiang, Kui Huang, Jinwoong

Hwang, Zhuojun Li, Choongyu Hwang, Zhongkai Liu, Dawei Shen, Jonathan Sobota,

Patrick Kirchmann, Jiamin Xue, Thomas P Devereaux, Sung-Kwan Mo, Zhi-Xun Shen, Shujie

Tang, "Signatures of excitonic insulating state in monolayer 1T-ZrTe2", arXiv:2201.11592.

Materials at Extreme Conditions

Manipulating materials with high pressure high temperature (HPHT) is powerful to drive new states of matter by tuning structure, correlation effect and competing degrees of freedom in materials. The tunability for various materials’ properties using HPHT makes it a distinctive tool to design functional materials such as superconductivity, solar cell and color center etc, addressing the cutting-edge research in condensed matter physics, energy science and quantum computing science.

Figure: a, Experimental high pressure high temperature phase diagram of perovskite CsPbI3; b-e, ab initio electronic structure calculations for the total energy and Gibbs energy differences of two phases of CsPbI3, taken from Ref[2].

Publications:

[1] Sulgiye Park, Iwnetim I. Abate, Jin Liu, Chenxu Wang, Jeremy E. P. Dahl, Robert M. K. Carlson,

Liuxiang Yang, Vitali B. Prakapenka, Eran Greenberg, Thomas P. Devereaux, Chunjing Jia,

Rodney C. Ewing, Wendy L. Mao, Yu Lin, "Facile diamond synthesis from lower diamondoids",

Science Advances 6 no. 8, eaay9405 (2020)

[2] Feng Ke*, Chenxu Wang*, Chunjing Jia* (*equal contribution), Nathan R. Wolf, Jiejuan Yan,

Shanyuan Niu, Matthew D. Smith, Thomas P. Devereaux, Hemamala I. Karunadasa, Wendy L.

Mao, Yu Lin, "Preservation of a black CsPbI3 perovskite phase to ambient conditions via pressure directed octahedral tilt", Nature Communications 12 (1), 1-8 (2021)

[3] Yan-Kai Tzeng, Feng Ke, Chunjing Jia, Yayuan Liu, Sulgiye Park, Mungo Frost, Xinxin Cai,

Wendy L. Mao, Rodney C. Ewing, Yi Cui, Thomas P. Devereaux, Yu Lin, Steven Chu, "Improving the creation of SiV centers in diamond via sub- pulsed annealing treatment", (submitted)