Quantum tunneling of semifluxons

TL;DR

This paper investigates quantum tunneling phenomena in a system of two semifluxons within a long Josephson junction, analyzing the conditions under which quantum effects dominate over classical behavior.

Contribution

It models semifluxon dynamics as a single particle in a double well potential and estimates parameters for quantum tunneling and crossover temperatures.

Findings

Quantum tunneling rate between states quantified

Classical-to-quantum crossover temperature estimated

Conditions for observable quantum effects identified

Abstract

We consider a system of two semifluxons of opposite polarity in a 0-pi-0 long Josephson junction, which classically can be in one of two degenerate states: up-down or down-up. When the distance $a$ between the 0-pi boundaries (semifluxon's centers) is a bit larger than the crossover distance $a_c$, the system can switch from one state to the other due to thermal fluctuations or quantum tunneling. We map this problem to the dynamics of a single particle in a double well potential and estimate parameters for which quantum effects emerge. We also determine the classical-to-quantum crossover temperature as well as the tunneling rate (energy level splitting) between the states up-down and down-up.