Nonequilibrium generation of charge defects in kagome spin ice under slow cooling

TL;DR

This study investigates the nonequilibrium behavior of kagome spin ice during slow cooling, revealing a power-law relationship between defect density and quench rate, explained by reaction kinetics without dynamical freezing.

Contribution

The paper provides the first large-scale simulation analysis of charge defect dynamics in kagome spin ice under slow cooling, linking defect density to cooling rate via reaction kinetics.

Findings

Defect density follows a power-law with quench rate.

No dynamical freezing occurs due to finite relaxation time.

Late-stage defect decay is algebraic and thermally driven.

Abstract

Kagome spin ice is one of the canonical examples of highly frustrated magnets. The effective magnetic degrees of freedom in kagome spin ice are Ising spins residing on a two-dimensional network of corner-sharing triangles. Due to strong geometrical frustration, nearest-neighbor antiferromagnetic interactions on the kagome lattice give rise to a macroscopic number of degenerate classical ground states characterized by ice rules. Elementary excitations at low temperatures are defect-triangles that violate the ice rules and carry an additional net magnetic charge relative to the background. We perform large-scale Glauber dynamics simulations to study the nonequilibrium dynamics of kagome ice under slow cooling. We show that the density of residual charge defects exhibits a power law dependence on the quench rate for the class of algebraic cooling protocols. The numerical results are well captured by the rate equation for the charge defects based on the reaction kinetics theory. As the relaxation time of the kagome ice phase remains finite, there is no dynamical freezing as in the Kibble-Zurek scenario. Instead, we show that the power-law behavior originates from a thermal excitation that decay algebraically with time at the late stage of the cooling schedule. Similarities and differences in quench dynamics of other spin ice systems are also discussed.