Kavli Affiliate: Zheng Zhu
| First 5 Authors: Ji-Si Xu, Zheng Zhu, Kai Wu, Zheng-Yu Weng,
| Summary:
A chiral spin liquid (CSL) phase has been recently reported in the Hubbard
model on a triangular lattice at half-filling. It emerges in an intermediate
coupling regime, which is sandwiched between a $120^circ$ antiferromagnetic
(AFM) phase and a metallic phase as a function of on-site repulsion $U$. In
this work, we examine how the charge fluctuation may cause the CSL and complex
phase diagram. We first identify an exact sign structure of the model at
arbitrary temperature, sample size, and doping, which is reduced from the
original Fermi exchange signs of the electrons by finite $U$. In particular,
the spin and charge degrees of freedom are generally entangled via the
phase-string in the sign structure. By precisely switching off such a
phase-string, the CSL phase is shown to disappear, with only the $120^circ$
AFM order remaining down to weak $U$ by a density matrix renormalization group
calculation. Here the charge fluctuation is effectively decoupled from the AFM
background, which is a $120^circ$ AFM order due to a geometric Berry phase in
the sign structure of the triangular lattice. General implications for the Mott
physics will also be discussed.
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