Quantum Many-Body Simulations of the 2D Fermi-Hubbard Model in Ultracold Optical Lattices

报告摘要：Understanding quantum many-body states of correlated electrons is one main theme in modern condensed matter physics. Given that the Fermi-Hubbard model, the prototype of correlated electrons, has been recently realized in ultracold optical lattices, it is highly desirable to have controlled numerical methodology to provide precise finite-temperature results upon doping, to directly compare with experiments. Here, we demonstrate the exponential tensor renormalization group (XTRG) algorithm [Phys. Rev. X 8, 031082 (2018)], complemented with independent determinant quantum Monte Carlo (DQMC) offer a powerful combination of tools for this purpose. XTRG provides full and accurate access to the density matrix and thus various spin and charge correlations, down to unprecedented low temperature of few percents of the fermion tunneling energy scale. We observe  excellent agreement with ultracold fermion measurements at both half-filling and finite-doping, including the sign-reversal behavior in spin correlations due to formation of magnetic polarons, and the attractive hole-doublon and repulsive hole-hole pairs that are responsible for the peculiar bunching and antibunching behaviors of the antimoments.
报告人简介：李伟，北京航空航天大学副教授/理论物理研究所副研究员。2006年本科毕业于北航，2011年博士毕业于中国科学院，2012-2015年在德国慕尼黑大学从事博士后科研工作，2015-2021年在北航物理学院工作，2021年调动至中国科学院理论物理研究所工作。主要研究领域是关联量子多体物理，发展了有限温度张量重正化群系列方法等。截止目前在包括Nature Commun., PRX, PRL等重要国际学术期刊上发表论文50余篇。