SU(4) Spin-Orbital Two-Leg Ladder, Square and Triangle Lattices

TL;DR

This paper applies a Schwinger boson mean field theory to SU(4) spin-orbital systems, revealing a spin-orbital liquid in ladders and long-range order in 2D lattices, with results aligning with recent numerical studies.

Contribution

It introduces a Schwinger boson mean field approach to analyze SU(4) spin-orbital models on various lattices, providing new insights into their ground states and ordering phenomena.

Findings

Ground state of two-leg SU(4) ladder is a spin-orbital liquid with a finite gap.

In 2D lattices, Bose condensation occurs at specific wave vectors leading to long-range order.

Static susceptibilities become singular at certain wave vectors, indicating ordering.

Abstract

Based on the generalized valence bond picture, a Schwinger boson mean field theory is applied to the symmetric SU(4) spin-orbital systems. For a two-leg SU(4) ladder, the ground state is a spin-orbital liquid with a finite energy gap, in good agreement with recent numerical calculations. In two-dimensional square and triangle lattices, the SU(4) Schwinger bosons condense at (\pi/2,\pi/2) and (\pi/3,\pi/3), respectively. Spin, orbital, and coupled spin-orbital static susceptibilities become singular at the wave vectors, twice of which the bose condensation arises at. It is also demonstrated that there are spin, orbital, and coupled spin-orbital long-range orderings in the ground state.