Electron energy spectrum of the spin-liquid state in a frustrated Hubbard model

TL;DR

This study investigates the electron energy spectrum in a frustrated Hubbard model on a triangular lattice, revealing how non-local correlations favor a spin liquid state with a larger energy gap compared to magnetic states.

Contribution

It introduces a dual fermion approach with k-dependent self-energy to analyze non-local correlations, highlighting the stabilization of the spin liquid state.

Findings

Dual fermion corrections lower the energy of the spin liquid state.

The spin liquid exhibits a larger energy gap than the 120° antiferromagnetic state.

The spin liquid becomes energetically favorable within a specific interaction strength range.

Abstract

Non-local correlation effects in the half-filled Hubbard model on an isotropic triangular lattice are studied within a spin polarized extension of the dual fermion approach. A competition between the antiferromagnetic non-collinear and the spin liquid states is strongly enhanced by an incorporation of a k-dependent self-energy beyond the local dynamical mean-field theory. The dual fermion correc- tions drastically decrease the energy of a spin liquid state while leaving the non-collinear magnetic states almost non-affected. This makes the spin liquid to become a preferable state in a certain interval of interaction strength of an order of the magnitude of a bandwidth. The spectral function of the spin-liquid Mott insulator is determined by a formation of local singlets which results in the energy gap of about twice larger than that of the 120 degrees antiferromagnetic Neel state.