A spin liquid with pinch-line singularities on the pyrochlore lattice

TL;DR

This paper reports the discovery of a novel spin liquid on the pyrochlore lattice characterized by pinch-line singularities, extending the concept of gauge theories and spin correlations beyond spin ice systems.

Contribution

It introduces a new type of spin liquid with tensor gauge fields and predicts pinch-line singularities, linking theoretical models to experimental observations in Tb$_2$Ti$_2$O$_7$.

Findings

Identification of a tensor gauge field in a spin liquid

Prediction of pinch-line singularities in neutron scattering

Connection to experimental data in Tb$_2$Ti$_2$O$_7$

Abstract

The mathematics of gauge theories lies behind many of the most profound advances in physics in the last 200 years, from Maxwell's theory of electromagnetism to Einstein's theory of general relativity. More recently it has become clear that gauge theories also emerge in condensed matter, a prime example being the spin ice materials which host an emergent electromagnetic gauge field. In spin ice, the underlying gauge structure is revealed by the presence of pinch-point singularities in neutron-scattering measurements. Here we report the discovery of a spin liquid where the low-temperature physics is naturally described by the fluctuations of a tensor field with a continuous gauge freedom. This gauge structure underpins an unusual form of spin correlations, giving rise to pinch-line singularities--- line-like analogues of the pinch-points observed in spin ice. Remarkably, these features may already have been observed in the pyrochlore material Tb$_2$Ti$_2$O$_7$.