Pinch Points and Kasteleyn Transitions: How Spin Ice Changes its Entropy

TL;DR

This paper explores how applying a tilted magnetic field to spin ice materials like Ho2Ti2O7 reveals critical phenomena and emergent gauge structures, demonstrating controllable entropy and Kasteleyn physics through neutron scattering.

Contribution

It demonstrates the manipulation of spin ice entropy and critical behavior using a tilted magnetic field, linking experimental neutron scattering results to theoretical Kasteleyn physics.

Findings

Observation of pinch point scattering indicating emergent gauge structure

Detection of diffuse peaks shifting with magnetic field, signaling Kasteleyn physics

Identification of an unusual critical point in spin ice under tilted field

Abstract

Complex disordered states - from liquids and glasses to exotic quantum matter - are ubiquitous in nature. Their key properties include finite entropy, power-law correlations and emergent organising principles. In spin ice, spin correlations are determined by an ice rules organising principle that stabilises a magnetic state with the same zero point entropy as water ice. The entropy can be manipulated with great precision by a magnetic field: with field parallel to the trigonal axis one obtains quasi two dimensional kagome ice which can be mapped onto a dimer model. Here we use a field tilted slightly away from the trigonal axis to control the dimer statistical weights and realise the unusual critical behaviour predicted by Kasteleyn. Neutron scattering on Ho2Ti2O7 reveals pinch point scattering that characterises the emergent gauge structure of kagome ice; diffuse peaks that shift with field, signaling the Kasteleyn physics; and an unusual critical point.