On the origin of the possible chiral spin liquid state of the triangular lattice Hubbard model

TL;DR

This paper explains the possible emergence of a chiral spin liquid in the triangular lattice Hubbard model using a Bosonic RVB framework, highlighting its topological features and limitations of mean field approaches.

Contribution

It introduces a Bosonic RVB description of the chiral spin liquid state, emphasizing the role of four-spin ring exchange and topological properties.

Findings

Chiral spin liquid can be viewed as a quantum disordered tetrahedral spin state.

The state exhibits a spin Berry phase of π/2 per triangle.

Schwinger Boson mean field theory misses the topological nature due to Boson rigidity issues.

Abstract

Recent numerical simulations find a possible chiral spin liquid state in the intermediate coupling regime of the triangular lattice Hubbard model. Here we provide a simple picture for its origin in terms of a Bosonic RVB description. More specifically, we show that such a chiral spin liquid state can be understood as a quantum disordered tetrahedral spin state stabilized by the four spin ring exchange coupling, which suppresses the order-by-disorder effect toward a stripy spin state. Such a chiral spin liquid state features a spin Berry phase of $\frac{\pi}{2}$ per triangle. However, we show that the topological property of such a state is totally missed in the Schwinger Boson mean field description as a result of the lack of Boson rigidity caused by the no double occupancy constraint.