Multiple Coulomb phases with temperature tunable ice rules in pyrochlore spin crossover materials

TL;DR

This paper demonstrates that elastic interactions in pyrochlore spin crossover materials can induce multiple temperature-tunable Coulomb phases with ice rules, revealing novel fractionalized excitations distinct from water or spin ices.

Contribution

It introduces a new mechanism for realizing multiple Coulomb phases in spin crossover materials through elastic interactions and temperature control.

Findings

Three distinct spin-state ice phases identified.

Temperature can tune between different Coulomb phases.

Low energy excitations exhibit spin fractionalization.

Abstract

Spin crossover molecules have two accessible states: high spin (HS) and low spin (LS). We show that, on the pyrochlore lattice, elastic interactions between SCO molecules can give rise to three spin-state ice phases. Each is a ``Coulomb phase'' where a local ice-rule can be mapped to a divergence free gauge field and the low energy excitations carry a spin fractionalized midway between the LS and HS states. The unique nature of spin crossover materials allows temperature to change the ice rules allowing straightforward access to Coulomb phases not yet observed in water or spin ices.