摘要

The BCS theory explains conventional superconductivity in terms of electrons with opposite spin and momentum that condense into pairs. A sufficiently large magnetic field destroys superconductivity by coupling to the orbital motion of the electrons. In 1964, Fulde & Ferrell and Larkin & Ovchinnikov (FFLO) showed that this coupling would give rise to a state different to the conventional BCS-state. In particular, this state may exhibit a spatially modulated order parameters as well as finite momentum of Cooper pairs. Up to now, the FFLO state is still elusive to experimental observation. In the talk, I will discuss our theoretical studies on the FFLO states of polarized fermions in cold atoms and condensed matter systems. First we investigate the superfluidity with imbalanced populations of harmonically trapped ultracold fermions in a 2D optical lattice. In the high-density regime, a novel FFLO state with gap oscillation along the angular direction shows up and the accompanying ferromagnetic order modulates accordingly. Next we study the electronic properties of a heterostructure consisting of ferromagnetic metallic layer and s-wave superconductor layer. We demonstrate that a novel stripe FFLO state as well as a 2D FFLO state may show up due to the proximity effect.

报告人简介

陈焱教授，1993年南京大学学士，1998年南京大学博士。1998年至2003年美国休斯顿大学德州超导中心博士后及Research Associate，2003年-2007年香港大学物理系助理教授(研究) ，2009年至今香港大学荣誉副教授。2007年至今为复旦大学先进材料实验室主任研究员。他主要从事凝聚态体系的理论研究。研究兴趣包括高温超导铜氧化物的电子态特性、超冷原子系统中的奇异超流态,量子纠缠与量子相变等。