主讲人：李宇 博士后（中国科学院大学）

报告题目：Two-stage superconductivity in Hatsugai-Kohmoto-BCS model

时间：2022年11月18日（周五）上午10：30

腾讯会议ID：620 158 698

联系人：钟 寅

报告摘要：

Superconductivity in strongly correlated electrons can emerge out from a normal state that is beyond the Landau’s Fermi liquid paradigm, often dubbed as “non-Fermi liquid”. While the theory for non-Fermi liquid is still not yet conclusive, a recent study on the exactly-solvable Hatsugai–Kohmoto (HK) model has suggested a non-Fermi liquid ground state whose Green’s function resembles the Yang–Rice–Zhang ansatz for cuprates (P. Phillips et al Nat. Phys. 16, 1175 (2020)). Similar to the effect of on-site Coulomb repulsion in the Hubbard model, the repulsive interaction in the HK model divides the momentum space into three parts: empty, single-occupied and double-occupied regions, that are separated from each other by an emergent “two Fermi surfaces” description. In this talk, I will show how these two Fermi surfaces exhibit the Cooper instability simultaneously. And then, in the presence of an additional Bardeen–Cooper–Schrieffer-type pairing interaction of a moderate strength, the system exhibits a novel ‘two-stage superconductivity’ feature as temperature decreases: a first-order superconducting transition occurs at a temperature Tc that is followed by a sudden increase of the superconducting order parameter at a lower temperature Tc′ < Tc. The phase transitions and the mechanisms are analyzed by the thermodynamic evolutions and the Ginzburg–Landau theory. Our work sheds new light on unconventional superconductivity in strongly correlated electrons.

个人简介：

李宇，2012年本科毕业于东华大学理学院，于2018年在中国科学院物理研究所获得博士学位。2019年-至今，于中国科学院大学卡弗里理论科学研究所从事博士后研究。主要研究领域涉及：重费米子超导的配对对称性研究，手征超导中的Kerr效应研究，以及非费米液体超导模型中的奇异超导性质探索等。