Xiao Yan Xu

xiaoyanxu@sjtu.edu.cn

Education

2012-2017 Ph.D. in Theoretical Physics, IOP, CAS

2008-2012 Bachelor's Degree in Physics, HUST

Experience

2023-Present Researcher, Hefei National Laboratory

2021-Present Associate Professor, SJTU

2019-2021 Postdoctoral Fellow, UC San Diego

2017-2019 Postdoctoral Fellow, Hong Kong UST   

Overview of Academic Research

Professor Xiao Yan Xu is primarily engaged in theoretical and computational research on strongly correlated electron systems, including quantum spin liquids, non-Fermi liquids, sign problems, quantum criticality, quantum entanglement, and interdisciplinary research at the intersection of quantum many-body physics with machine learning, quantum information, and ultracold atomic physics. The following important achievements have been made:

(1) Successfully predicted that monolayer 1T-TaS₂ and other systems are quantum spin liquid candidates;

(2) conducted a series of original research on sign problems, proposed pseudo-unitary group theory to solve a class of sign problems, advanced research on U(1) gauge field coupling with fermions, first discovered algebraic sign behavior, and proposed sign bounds theory, solving sign problems in multiple strongly correlated electron microscopic models and discovering novel phases and phase transitions therein;

(3) proposed novel Monte Carlo algorithms such as self-learning Monte Carlo and momentum-space Monte Carlo, developed determinant Monte Carlo update algorithms including delayed updates and submatrix updates, and discovered power-law relationships between self-energy and frequency at itinerant ferromagnetic quantum critical points through numerically exact calculations, which has been verified by international peers; first proposed a quantum Monte Carlo method for calculating Rényi entanglement negativity in correlated fermion systems, advancing research on fermionic many-body mixed-state entanglement.

Research Directions:

Novel phases such as non-Fermi liquids and quantum spin liquids

Many-body quantum entanglement and quantum criticality

Sign problems and development of quantum many-body computational methods

Major Honors and Awards

2022 National Science Fund for Excellent Young Scholars (Overseas)

Representative Publications

[1] Xiao Yan Xu, Yang Qi, Junwei Liu, Liang Fu, Zi Yang Meng. Self-learning quantum Monte Carlo method in interacting fermion systems.  Phys. Rev. B 96, 041119(R) (2017)

[2] Xiao Yan Xu, Kai Sun, Yoni Schattner, Erez Berg, Zi Yang Meng. Non-Fermi Liquid at (2+1)D Ferromagnetic Quantum Critical Point.  Phys. Rev. X 7, 031058 (2017)

[3] Chuang Chen, Xiao Yan Xu*, Junwei Liu, George Batrouni, Richard Scalettar, Zi Yang Meng*. Symmetry-enforced self-learning Monte Carlo method applied to the Holstein model. Phys. Rev. B 98, 041102(R) (2018)

[4] Wen-Yu He, Xiao Yan Xu*, Gang Chen, K. T. Law*, Patrick A. Lee*. Spinon Fermi Surface in a Cluster Mott Insulator Model on a Triangular Lattice and Possible Application to 1T-TaS2.  Phys. Rev. Lett. 121, 046401 (2018)

[5] Xiao Yan Xu, K. T. Law, Patrick A. Lee. Kekulé valence bond order in an extended Hubbard model on the honeycomb lattice, with possible applications to twisted bilayer graphene.  Phys. Rev. B 98, 121406(R) (2018). Editors' Suggestion

[6] Xiao Yan Xu*, Yang Qi*, Long Zhang, Fakher F. Assaad, Cenke Xu, Zi Yang Meng*. Monte Carlo Study of Compact Quantum Electrodynamics with Fermionic Matter: the Parent State of Quantum Phases.  Phys. Rev. X 9, 021022 (2019)

[7] Zi Hong Liu, Gaopei Pan, Xiao Yan Xu, Kai Sun, Zi Yang Meng. Itinerant Quantum Critical Point with Fermion Pockets and Hot Spots. Proceedings of the National Academy of Sciences 116, 16760 (2019)

[8] Chuang Chen, Xiao Yan Xu, Zi Yang Meng, Martin Hohenadler. Charge-Density-Wave Transitions of Dirac Fermions Coupled to Phonons.  Phys. Rev. Lett. 122, 077601 (2019)

[9] Xiao Yan Xu*, K. T. Law*, Patrick A. Lee*. Pair Density Wave in the doped t-J model with ring exchange on a triangular lattice.  Phys. Rev. Lett. 122, 167001 (2019)

[10] Yuan Da Liao, Zi Yang Meng, Xiao Yan Xu*. Valence Bond Orders at Charge Neutrality in a Possible Two-Orbital Extended Hubbard Model for Twisted Bilayer Graphene.  Phys. Rev. Lett. 123, 157601 (2019)

[11] Lukas Janssen, Wei Wang, Michael M. Scherer, Zi Yang Meng, Xiao Yan Xu. Confinement transition in the QED3-Gross-NeveuXY universality class.  Phys. Rev. B 101, 235118 (2020)

[12] Xiao Yan Xu*, Avraham Klein, Kai Sun, Andrey V. Chubukov, Zi Yang Meng*. Identification of non-Fermi liquid fermionic self-energy from quantum Monte Carlo data. npj Quantum Mater. 5, 65 (2020)

[13] Yuan Da Liao, Jian Kang, Clara N. Breiø, Xiao Yan Xu, HanQing Wu, Brian M. Andersen, Rafael M. Fernandes, Zi Yang Meng. Correlation-induced insulating topological phases at charge neutrality in twisted bilayer graphene. Phys. Rev. X 11, 011014 (2021)

[14] Ying-Ming Xie, Xue-Jian Gao, Xiao Yan Xu, Cheng-Ping Zhang, Jin-Xin Hu, K. T. Law. Kramers Nodal Line Metals. Nature Communications 12, 3064 (2021)

[15] Xiao Yan Xu, Tarun Grover. Competing Nodal d-Wave Superconductivity and Antiferromagnetism. Phys. Rev. Lett. 126, 217002 (2021)

[16] Yunqing Ouyang, Xiao Yan Xu*. Projection of Infinite-U Hubbard Model and Algebraic Sign Structure. Phys. Rev. B 104, L241104 (2021)

[17] Xu Zhang, Gaopei Pan, Xiao Yan Xu*, Zi Yang Meng*. Fermion sign bounds theory in quantum Monte Carlo simulation. Phys. Rev. B 106, 035121 (2022)

[18] Xiao Yan Xu, Tarun Grover. Fermionic skyrmions and bosonization for a Gross-Neveu transition. Phys. Rev. B 109, 155112 (2024)

[19] Fanjie Sun, Xiao Yan Xu*. Delay update in determinant quantum Monte Carlo. Phys. Rev. B 109, 235140 (2024)

[20] Fo-Hong Wang, Xiao Yan Xu*. Entanglement Rényi negativity of interacting fermions from quantum Monte Carlo simulations. Nature Communications 16, 2637 (2025)

[21] Zenan Dai, Xiao Yan Xu*. Residual entropy from the temperature incremental Monte Carlo method. Phys. Rev. B 111, L081108 (2025)

[22] Fanjie Sun, Xiao Yan Xu*. Boosting determinant quantum Monte Carlo with submatrix updates: Unveiling the phase diagram of the 3D Hubbard model. SciPost Phys. 18, 055 (2025)

[23] Tu Hong, Xiao Yan Xu*. Monte Carlo Study of Critical Fermi Surface with Spatially Disordered Interactions. arXiv:2410.13858

[24] Fo-Hong Wang, Xiao Yan Xu*. Untwisted and Twisted Rényi Negativities: Toward a Rényi Proxy for Logarithmic Negativity in Fermionic Systems. arXiv:2503.07731

[25] Jun Qi Fang, Xiao Yan Xu*. Fermionic Partial Transpose in the Overlap Matrix Framework for Entanglement Negativity. arXiv:2503.07742

[26] Haiyang Chen#, Fo-Hong Wang#, Qiang Gao, Xue-Jian Gao, Zhenhua Chen, Yaobo Huang, Kam Tuen Law, Xiao Yan Xu*, Peng Chen*. Spectroscopic evidence for possible quantum spin liquid behavior in a two-dimensional Mott insulator. Phys. Rev. Lett. 134, 066402 (2025)