Schwinger boson mean field theory: numerics for the energy landscape and gauge excitations in two-dimensional antiferromagnets

TL;DR

This paper systematically explores Schwinger boson mean field states on square and triangular lattices, identifying gauge modes, topological degeneracy, and vison states in different phases of two-dimensional antiferromagnets.

Contribution

It provides a comprehensive numerical analysis of the energy landscape and gauge excitations in Schwinger boson mean field theory for 2D antiferromagnets, including inhomogeneous states and saddle points.

Findings

Gapless U(1) gauge modes in the square lattice non-magnetic phase

Topological degeneracy and vison states in the triangular lattice Z_2 liquid phase

Identification of low-energy saddle points and inhomogeneous ground states

Abstract

We perform some systematic numerical search for Schwinger boson mean field states on square and triangular lattice clusters. We look for possible inhomogeneous ground states as well as low-energy excited saddle points. The spectrum of the Hessian is also computed for each solution. On the square lattice we find gapless U(1) gauge modes in the non-magnetic phase. In the Z_2 liquid phase of the triangular lattice we identify the topological degeneracy as well as vison states.