（California State University, Northridge）

摘要：Understanding the interplay of geometry frustration and electron correlation is one of the central topics of the modern condensed matter physics.  The emergence of the topological phases has been established through examples of exact solvable models. The central open question is regarding what topological phases can be realized in experimental relevant systems.

In this talk I will focus on different spin liquid states on frustrated triangular lattice spin model, and a nontrivial spin current state in doped t-J model on square lattice.  For triangular lattice model, I will present numerical evidence supporting a new state of matter, which breaks time-reversal symmetry spontaneously, and also has low energy excitations consistent with a spinon Fermi-Sea state.  Theoretical understanding of the exotic state will be presented based on a staggered flux phase at mean-field level.  For doped t-J model on square lattice, we will demonstrate a new fractionalized state, which has emergence of the nontrivial spin current.  We will compare the physics of such a state with the variational wavefunction constructed based on the  phase string theory of the doped t-J model, which naturally leads to hole pairing for finite doping. We will conclude my talk with discussions of   open questions and future directions in this field.

邀请人：张龙

联系人：方辰（82649073）