Neel order, quantum spin liquids and quantum criticality in two dimensions

TL;DR

This paper explores the possibility of a direct second order quantum phase transition from a Neel ordered phase to a spin liquid in two-dimensional quantum antiferromagnets, with implications for understanding cuprate superconductors.

Contribution

It proposes a theoretical framework for a second order transition to certain spin liquids, challenging conventional wisdom and studying its universal properties via an epsilon expansion.

Findings

Second order transitions to spin liquids are possible in 2D antiferromagnets.

The theory clarifies how antiferromagnetic order can be incorporated into spin liquid models.

Implications for the understanding of underdoped cuprates are discussed.

Abstract

This paper is concerned with the possibility of a direct second order transition out of a collinear Neel phase to a paramagnetic spin liquid in two dimensional quantum antiferromagnets. Contrary to conventional wisdom, we show that such second order quantum transitions can potentially occur to certain spin liquid states popular in theories of the cuprates. We provide a theory of this transition and study its universal properties in an $\epsilon$ expansion. The existence of such a transition has a number of interesting implications for spin liquid based approaches to the underdoped cuprates. In particular it considerably clarifies existing ideas for incorporating antiferromagnetic long range order into such a spin liquid based approach.