Melting upon cooling in a quantum magnet
Abstract
Heating enhances thermal fluctuations and typically leads to melting of solids, but in exceptional cases, heating can also cause liquids to solidify. The paradigm of this counterintuitive phenomenon is solidification of liquid He upon increasing temperature, known as the Pomeranchuk effect. Here we show that such inverse melting also appears in quantum magnetism. We find that, on cooling, the Ising-like triangular-lattice antiferromagnet erbium heptatantalate first develops a three-sublattice long-range magnetic order -- analogous to a solid -- which then, unexpectedly, melts at even lower temperatures into a short-range correlated spin-stripe state -- analogous to a liquid. We propose that such an unprecedented ``spin Pomeranchuk effect" can generically arise from strong competition between spin-spin interactions in frustrated magnets, and provides a novel avenue to transformations between exotic magnetic phases.
Cite
@article{arxiv.2605.04611,
title = {Melting upon cooling in a quantum magnet},
author = {K. Jaksetič and T. Arh and M. Pregelj and M. Gomilšek and M. Dragomir and P. Prelovšek and M. Ulaga and L. Šibav and M. Malovrh and K. Železnikar and Z. Jagličić and P. Manuel and F. Orlandi and D. Khalyavin and M. D. Le and N. Bujault and E. Lhotel and J. van Tol and U. Jena and B. Sana and P. Khuntia and A. Zorko},
journal= {arXiv preprint arXiv:2605.04611},
year = {2026}
}