Competing Gauge Fields and Entropically-Driven Spin Liquid to Spin Liquid Transition in non-Kramers Pyrochlores

TL;DR

This paper explores how competing gauge fields influence temperature-driven phase transitions in non-Kramers pyrochlore spin liquids, revealing coexistence of gauge fields and entropic effects that shape the system's behavior.

Contribution

It introduces a novel framework for understanding temperature-dependent spin liquid phases with coexisting gauge fields in pyrochlore lattices, supported by numerical evidence.

Findings

Coexistence of vector and matrix gauge fields in intermediate temperature regimes.

Entropic selection leads to spin ice-like behavior at low temperatures.

Quantum models show a stable spin liquid phase with coexisting gauge fields at zero temperature.

Abstract

Gauge theories are powerful tools in theoretical physics, allowing complex phenomena to be reduced to simple principles, and are used in both high-energy and condensed matter physics. In the latter context, gauge theories are becoming increasingly popular for capturing the intricate spin correlations in spin liquids, exotic states of matter in which the dynamics of quantum spins never ceases, even at absolute zero temperature. We consider a spin system on a three-dimensional pyrochlore lattice where emergent gauge fields not only describe the spin liquid behaviour at zero temperature but crucially determine the system's temperature evolution, with distinct gauge fields giving rise to different spin liquid phases in separate temperature regimes. Focusing first on classical spins, in an intermediate temperature regime, the system shows an unusual coexistence of emergent vector and matrix gauge fields where the former is known from classical spin ice systems while the latter has been associated with fractonic quasiparticles, a peculiar type of excitation with restricted mobility. Upon cooling, the system transitions into a low-temperature phase where an entropic selection mechanism depopulates the degrees of freedom associated with the matrix gauge field, rendering the system spin ice like. We further provide numerical evidence that in the corresponding quantum model, a spin liquid with coexisting vector and matrix gauge fields has a finite window of stability in the parameter space of spin interactions down to zero temperature. Finally, we discuss the relevance of our findings for non-Kramers pyrochlore materials.