The Existence of Featureless Paramagnets on the Square and the Honeycomb Lattices in 2+1D

TL;DR

This paper investigates the theoretical possibility of featureless paramagnets on 2D lattices, proposing new wave functions and verifying their properties, thus expanding understanding of quantum magnetic phases.

Contribution

It introduces a generalized 'slave-spin' construction for featureless paramagnets and verifies their existence on certain 2D lattices through analytical and numerical methods.

Findings

Featureless wave functions constructed for spin-1 square and honeycomb lattices.

Analytical and numerical verification of featureless states for spin-1 cases.

Uncertain status of spin-1/2 honeycomb featureless state.

Abstract

The peculiar features of quantum magnetism sometimes forbid the existence of gapped `featureless' paramagnets which are fully symmetric and unfractionalized. The Lieb-Schultz-Mattis theorem is an example of such a constraint, but it is not known what the most general restriction might be. We focus on the existence of featureless paramagnets on the spin-1 square lattice and the spin-1 and spin-1/2 honeycomb lattice with spin rotation and space group symmetries in 2+1D. Although featureless paramagnet phases are not ruled out by any existing theorem, field theoretic arguments disfavor their existence. Nevertheless, by generalizing the construction of Affleck, Kennedy, Lieb and Tasaki to a class we call `slave-spin' states, we propose featureless wave functions for these models. The featureless-ness of the spin-1 slave-spin states on the square and honeycomb lattice are verified both analytically and numerically, but the status of the spin-1/2 honeycomb state remains unclear.