Spin-state ice in geometrically frustrated spin-crossover materials

TL;DR

This paper introduces the concept of spin-state ice in geometrically frustrated spin-crossover materials, where elastic interactions lead to a disordered phase with emergent gauge fields and fractionalized excitations.

Contribution

It proposes a novel phase called spin-state ice arising from frustration in spin-crossover materials, with a theoretical framework describing its emergent gauge fields and excitations.

Findings

Spin-state ice phases can emerge in frustrated spin-crossover materials.

The low-energy physics involves an emergent divergence-less gauge field.

Deconfined quasi-particles exhibit spin fractionalization.

Abstract

Spin crossover materials contain metal ions that can access two spin-states: one low-spin (LS), the other high-spin (HS). We propose that frustrated elastic interactions can give rise to spin-state ices -- phases of matter without long-range order, characterized by a local constraint or `ice rule'. The low-energy physics of spin-state ices is described by an emergent divergence-less gauge field with a gap to topological excitations that are deconfined quasi-particles with spin fractionalized midway between the spins of the LS and HS states.