The modulated spin liquid: a new paradigm for URu$_2$Si$_2$

TL;DR

This paper proposes a modulated spin liquid state near a Kondo breakdown critical point as a candidate for the hidden order phase in URu$_2$Si$_2$, highlighting its phase transition properties and symmetry breaking features.

Contribution

It introduces a new modulated spin liquid phase that breaks $Z_4$ symmetry and competes with antiferromagnetic order, providing a novel explanation for URu$_2$Si$_2$'s hidden order.

Findings

The modulated spin liquid forms via a second order phase transition.

It quenches entropy similarly to antiferromagnetic ordering.

It exhibits $Z_4$ symmetry breaking consistent with experimental observations.

Abstract

We argue that near a Kondo breakdown critical point, a spin liquid with spatial modulations can form. Unlike its uniform counterpart, we find that this occurs via a second order phase transition. The amount of entropy quenched when ordering is of the same magnitude as for an antiferromagnet. Moreover, the two states are competitive, and at low temperatures are separated by a first order phase transition. The modulated spin liquid we find breaks $Z_4$ symmetry, as recently seen in the hidden order phase of URu$_2$Si$_2$. Based on this, we suggest that the modulated spin liquid is a viable candidate for this unique phase of matter.