Quantum Phase Transitions around the Staggered Valence Bond Solid

TL;DR

This paper investigates quantum phase transitions involving Z_2 spin liquids, Neel order, and staggered VBS states on honeycomb and square lattices, revealing different order parameter descriptions for staggered VBS.

Contribution

It provides a novel description of staggered VBS as an O(3)/CP(2) or O(4)/CP(3) order parameter with cubic anisotropy, contrasting with the columnar VBS.

Findings

Staggered VBS on honeycomb lattice described by O(3)/CP(2) with cubic anisotropy.

Staggered VBS on square lattice described by O(4)/CP(3).

Different order parameter frameworks for staggered versus columnar VBS.

Abstract

Motivated by recent numerical results, we study the quantum phase transitions between Z_2 spin liquid, Neel ordered, and various valence bond solid (VBS) states on the honeycomb and square lattices, with emphasis on the staggered VBS. In contrast to the well-understood columnar VBS order, the staggered VBS is not described by an XY order parameter with Z_N anisotropy close to these quantum phase transitions. Instead, we demonstrate that on the honeycomb lattice, the staggered VBS is more appropriately described as an O(3) or CP(2) order parameter with cubic anisotropy, while on the square lattice it is described by an O(4) or CP(3) order parameter.