Interference of Instanton Trajectories in Quantum Tunneling for Small Particles of Real Antiferromagnets

TL;DR

This paper investigates how instanton interference affects quantum tunneling in small antiferromagnetic particles, considering symmetry and Dzyaloshinskii-Moriya interactions, revealing suppression effects and a periodic dependence of energy level splitting.

Contribution

It introduces a detailed analysis of instanton interference in antiferromagnets, incorporating Berry phase, symmetry, and Dzyaloshinskii-Moriya interaction effects, which was not comprehensively addressed before.

Findings

Destructive instanton interference can suppress tunneling.

Ground-state level splitting depends periodically on Dzyaloshinskii-Moriya interaction.

The magnitude of level splitting is explicitly calculated.

Abstract

For a two-sublattice antiferromagnet the Lagrangian is constructed taking into account Berry phase whose form is matched to the quantum-mechanical Heisenberg Hamiltonian. Tunnel effects are analyzed taking into account the crystallographic symmetry and possible types of the Dzyaloshinskii-Moriya interaction. It is shown that, when the real magnetic symmetry and the Dzyaloshinskii-Moriya interaction are taken into consideration, the effects of a destructive instanton interference and the suppression of macroscopic quantum tunneling can play an essential role. It also may lead to a periodic dependence of the ground-state level splitting on the Dzyaloshinskii-Moriya interaction constant; the magnitude of this splitting is calculated.