Speaker: Prof. Xi-Wen Guan (Wuhan Institute of Phys. & Math., Chinese Academy of Sciences)

Time: 3:00pm, Thursday, May 16, 2013

Venue: Conference Hall 104, Science Building, Tsinghua University

Abstract: Typical exactly solved models always involve very complicated Bethe ansatz equations which often scare physicists from other fields away. However, such complex Bethe ansatz equations, describing individual motions of particles, uniquely acquire a certain simple form of universality. In this talk, we discuss Wislon ratio of a one-dimensional (1D) Fermi gas (the Yang-Gaudin model) with spin imbalance. We find that the Wilson ratio, i.e., a ratio of spin susceptibility to specific heat divided out the temperature, is an interaction-dependent dimensionless constant that elegantly quantifies a two-component Tomonaga-Luttinger liquid (TLL) in the attractive Fermi gas at low temperatures. Breakdown of the universal Wilson ratio characterizes quantum criticality of the gas near the critical point. For repulsive regime, the Wilson ratio simply gives a fixed point of TLL in a scenario of spin-charge separation. We remark that our analysis can be adapted to capture a universal nature of multi-component TLLs in 1D interacting fermions of cold atoms with higher spin symmetry.