Supercooling and fragile glassiness in a dipolar kagome Ising magnet

TL;DR

This paper investigates a disorder-free dipolar kagome Ising magnet, revealing a first-order phase transition, supercooled liquid behavior, and fragile glassiness with super-Arrhenius dynamics, akin to glass-forming liquids.

Contribution

It demonstrates a disorder-free, realisable model exhibiting fragile glassiness and supercooled dynamics, expanding understanding of glassy behavior without quenched disorder.

Findings

Identifies a first-order transition to an ordered state with a 12-site unit cell.

Shows super-Arrhenius relaxation behavior above the transition.

Finds divergence of relaxation time following Vogel-Fulcher law at finite temperature.

Abstract

We study equilibration and ordering in the classical dipolar kagome Ising antiferromagnet, which we show behaves as a disorder-free fragile spin glass. By identifying an appropriate order parameter, we demonstrate a transition to the ordered state proposed by Chioar et al. [Phys. Rev. B 93, 214410 (2016)] with a 12-site unit cell that breaks time-reversal and sublattice symmetries, and further provide evidence that the nature of the transition is first order. Upon approaching the transition, the spin dynamics slow dramatically. The system readily falls out of equilibrium, overshooting the transition and entering a supercooled liquid regime. Using extensive Monte Carlo simulations, we show that the system exhibits super-Arrhenius behaviour above the ordering transition. The relaxation time diverges according to a Vogel-Fulcher form at a finite `glass transition' temperature in the supercooled regime. Such behaviour, characteristic of fragile glasses, is particularly remarkable as the model is free of quenched disorder, does not straightforwardly conform to the avoided criticality paradigm, and is simple and eminently realisable in engineered nanomagnetic arrays.