Spin-orbital gapped phase with least symmetry breaking in the one-dimensional symmetrically coupled spin-orbital model

TL;DR

This paper introduces a mean field theory for a one-dimensional spin-orbital model, revealing a spin-orbital gapped phase with minimal symmetry breaking and a crossover from coherent to incoherent magnetic excitations.

Contribution

It presents a simple SU(4) constraint fermion mean field approach to describe the spin-orbital gap formation and excitation behavior in the model.

Findings

Energy gap grows slowly from the SU(4) point and then decreases rapidly.

Crossover from coherent to incoherent magnetic excitations as coupling decreases.

Spin, orbital, and tensor susceptibilities indicate the nature of excitations.

Abstract

To describe the spin-orbital energy gap formation in the one-dimensional symmetrically coupled spin-orbital model, we propose a simple mean field theory based on an SU(4) constraint fermion representation of spins and orbitals. A spin-orbital gapped phase is formed due to a marginally relevant spin-orbital valence bond pairing interaction. The energy gap of the spin and orbital excitations grows extremely slowly from the SU(4) symmetric point up to a maximum value and then decreases rapidly. By calculating the spin, orbital, and spin-orbital tensor static susceptibilities at zero temperature, we find a crossover from coherent to incoherent magnetic excitations as the spin-orbital coupling decreasing from large to small values.