Quantum Tunneling and Phase Transitions in Spin Systems with an Applied Magnetic Field

TL;DR

This paper investigates quantum tunneling and phase transitions in spin systems with an applied magnetic field, revealing how anisotropy and magnetic parameters influence the nature of these transitions.

Contribution

It introduces an effective Lagrangian framework to analyze how asymmetry and external magnetic fields affect quantum and classical phase transitions in spin systems.

Findings

Transitions can be first- or second-order depending on system parameters

Asymmetry due to magnetic field influences the energy barrier dynamics

Effective Lagrangian describes the transition behavior

Abstract

Transitions from classical to quantum behaviour in a spin system with two degenerate ground states separated by twin energy barriers which are asymmetric due to an applied magnetic field are investigated. It is shown that these transitions can be interpreted as first- or second-order phase transitions depending on the anisotropy and magnetic parameters defining the system in an effective Lagrangian description.