Thermodynamics and fractal dynamics of nematic spin ice, a doubly frustrated pyrochlore Ising magnet

TL;DR

This paper explores a novel frustrated pyrochlore Ising magnet exhibiting combined frustration effects, a nematic phase transition, extensive degeneracy, and anomalous fractal monopole dynamics at low temperatures.

Contribution

It demonstrates the coexistence of different frustration mechanisms in a single system and characterizes a new nematic phase with unique dynamical properties.

Findings

First order phase transition to a nematic frustrated phase

Extensive degeneracy persists down to zero temperature

Anomalous noise from fractal monopole motion

Abstract

The Ising antiferromagnets on the triangular and on the pyrochlore lattices are two of the most iconic examples of magnetic frustration, paradigmatically illustrating many exotic properties such as emergent gauge fields, fractionalisation, and topological order. In this work, we show that the two instances of frustration can, remarkably, be combined in a single system, where they coexist without inducing conventional long range ordering. We show that the system undergoes a first order phase transition upon lowering the temperature, into a yet different frustrated phase that we characterise to exhibit nematic order. We argue that an extensive degeneracy survives down to zero temperature, at odds with a customary Pauling estimate. Dynamically, we find evidence of anomalous noise in the power spectral density, arising from an effectively anisotropic fractal motion of monopoles at low temperature.