Thermally activated escape rates of uniaxial spin systems with transverse field

TL;DR

This paper investigates the escape rates of uniaxial spin systems under transverse fields, revealing new crossover behaviors between different damping regimes through analytical and numerical methods.

Contribution

It provides the first analytical and numerical analysis of crossover phenomena in spin systems with transverse fields, expanding understanding of damping regimes.

Findings

Identification of a high-damping to uniaxial crossover.

Discovery of two low-damping crossovers separating regimes.

Characterization of energy saddle points introduced by transverse fields.

Abstract

Classical escape rates of uniaxial spin systems are characterized by a prefactor differing from and much smaller than that of the particle problem, since the maximum of the spin energy is attained everywhere on the line of constant latitude: theta=const, 0 =< phi =< 2*pi. If a transverse field is applied, a saddle point of the energy is formed, and high, moderate, and low damping regimes (similar to those for particles) appear. Here we present the first analytical and numerical study of crossovers between the uniaxial and other regimes for spin systems. It is shown that there is one HD-Uniaxial crossover, whereas at low damping the uniaxial and LD regimes are separated by two crossovers.