Quantum Signatures of The Classical Disconnection Border

TL;DR

This paper investigates quantum signatures of the classical energy disconnection border in a quantum Heisenberg model, revealing quantum tunneling effects that enable magnetization reversal below the classical border.

Contribution

It introduces a quantum disconnection border concept and analyzes its dynamical significance, including quantum tunneling effects on magnetic reversal.

Findings

Quantum tunneling allows magnetization flip below the classical EDB.

A quantum disconnection border is defined based on quantum regime considerations.

Time scales for magnetic reversal are evaluated using spectral properties.

Abstract

A quantum Heisenberg model with anisotropic coupling and all-to-all interaction has been analyzed using the Bose-Einstein statistics. In Ref.\cite{jsp} the existence of a classical energy disconnection border (EDB) in the same kind of models has been demonstrated. We address here the problem to find quantum signatures of the EDB. An independent definition of a quantum disconnection border, motivated by considerations strictly valid in the quantum regime is given. We also discuss the dynamical relevance of the quantum border with respect to quantum magnetic reversal. Contrary to the classical case the magnetization can flip even below the EDB through Macroscopic Quantum Tunneling. We evaluate the time scale for magnetic reversal from statistical and spectral properties, for a small number of particles and in the semiclassical limit.