报告时间：2022年5月25日（星期三）13：30

报告地点：勤园20-518

报告简介：

How interactions turn a partially filled electron band into an insulating state is an important question of strong correlation physics. We perform extensive projector determinant quantum Monte-Carlo (QMC) simulations on the SU(N) Hubbard models to address this problem. At half-filling, i.e., the average fermion number N/2 per site, the antiferromagnetic (AF) orders in the square lattice start from the weak U-regime for both SU(4) and SU(6) cases. They exhibit non-monotonic dependence on U: After reaching maxima at intermediate interaction strengths, they decrease as U further increases. The single-particle gap evolves from very small values to linearly increase with U, marking the onset of Mott physics. For the SU(6) case, the AF order vanishes at the critical value of U=13.3 exhibiting the critical exponents of ν=0.60 and η=0.44. As U further increases, the valence bond solid (VBS) ordering appears. We also investigated how interaction effects scale with N in the 1D SU(N) Hubbard models at half-filling. As N increases, weak and strong interacting systems are driven to a crossover region, but from opposite directions as a convergence of itinerancy and Mottness. The crossover region exhibits universalities such as nearly N-independent relative bandwidth, Fermi distribution, and the spin structure factor.

If time permits, I will also talk about the Curie-Weiss metal state and the critical region based on a multi-band Hubbard model, which to our knowledge, is the first QMC simulation to itinerant ferromagnetism without the sign problem.

Ref.

1. Han Xu, Yu Wang, Zhichao Zhou Congjun Wu, arxiv:‪1912.11791 .

2. Shenglong Xu, Julio T. Barreiro, Yu Wang, and C. Wu, Phys. Rev. Lett. 121, 167205 (2018).

3. Zhichao Zhou, Da Wang, Zi Yang Meng, Yu Wang, C. Wu, Phys. Rev. B 93, 245157 (2016)

4. Shenglong Xu, Yi Li, Congjun Wu, Phys. Rev. X 5, 021032, (2015)

5. D. Wang, Y. Li, Z. Cai, Z. Zhou, Y. Wang, C. Wu, Phys. Rev. Lett. 112, 156403 (2014).

报告人简介：

    吴从军教授于2005年获斯坦福大学博士学位; ‪2005-2007年于加州大学圣芭芭拉分校做博士后; ‪2007-2021年于加州大学圣迭戈分校历任助理教授、副教授、教授; 2021年于西湖大学理学院任讲席教授至今。2008年获斯隆研究奖；2018年美国物理学会会士(APS Fellow)。研究方向：强关联物理、拓扑物理、轨道物理、超导、量子磁性、冷原子物理，量子蒙特卡洛模拟。