Quantum tunneling between paramagnetic and superconducting states of a nanometer-scale superconducting grain placed in a magnetic field

TL;DR

This paper investigates quantum tunneling between superconducting and paramagnetic states in a nanometer-scale grain within a magnetic field, analyzing the tunneling probability via the instanton method considering the grain's environment.

Contribution

It introduces a theoretical framework for calculating quantum tunneling probabilities between states in a nanoscale superconducting grain in a magnetic field.

Findings

Derived an expression for tunneling probability in terms of magnetic field and system parameters.

Identified the role of the tunneling junction conductance in the quantum transition.

Provided insights into the quantum behavior of nanoscale superconducting systems.

Abstract

We consider the process of quantum tunneling between the superconducting and paramagnetic states of a nanometer-scale superconducting grain placed in a magnetic field. The grain is supposed to be coupled via tunneling junction to a normal metallic contact that plays a role of the spin reservoir. Using the instanton method we find the probability of the quantum tunneling process and express it in terms of the applied magnetic field, order parameter of the superconducting grain and conductance of the tunneling junction between the grain and metallic contact.