Resonant quantum coherence of magnetization at excited states in nanospin systems with different crystal symmetries

TL;DR

This paper theoretically investigates quantum interference effects, specifically Berry phase-induced resonant coherence, in excited states of nanospin systems with various crystal symmetries, revealing how these effects influence magnetization dynamics.

Contribution

It introduces a theoretical framework using the periodic instanton method to analyze tunnel splittings and energy spectra in excited states of nanospin systems with different symmetries.

Findings

Evaluation of low-lying tunnel splittings between degenerate excited states

Derivation of energy level spectra using Bloch theorem in periodic potentials

Insights into quantum interference effects in nanospin magnetization

Abstract

The quantum interference effects induced by the Wess-Zumino term, or Berry phase are studied theoretically in resonant quantum coherence of magnetization vector between degenerate excited states in nanometer-scale single-domain ferromagnets in the absence of an external magnetic field. By applying the periodic instanton method in the spin-coherent-state path integral, we evaluate the low-lying tunnel splittings between degenerate excited states of neighboring wells. And the low-lying energy level spectrum of m-th excited states are obtained with the help of the Bloch theorem in one-dimensional periodic potential.