Multiple Coulomb phases with temperature-tunable ice rules in pyrochlore spin-crossover materials
Year: 2021
Type: article
Abstract: Spin-crossover (SCO) molecules have two accessible states: one high spin (HS) and one low spin (LS). We show that on the pyrochlore lattice elastic interactions between SCO molecules can give rise to three different spin-state ice phases (denoted ${\text{H}}_{n}{\text{L}}_{4\ensuremath{-}n}$ with $n=1, 2, \mathrm{or} 3)$---characterized by the ``ice rules'' that every tetrahedron must contain $n$ HS and $4\ensuremath{-}n$ LS metals. 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. To date, no phase with the $n=1$ and $n=3$ ice rules has been observed. In SCO materials, the subtle competition between the entropies and enthalpies of the HS and LS states allows temperature or pressure to change the ice rules, allowing straightforward access to the $n=1$ and $n=3$ phases.
Authors: Jace Cruddas, B. J. Powell
Institution: The University of Queensland
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funder: Australian Research Council
OpenAlex ID: W3045535985