Quantum tunneling of vortices in a MgB$_2$ superconductor

TL;DR

This study investigates quantum tunneling of vortices in MgB$_2$ superconductors through magnetic relaxation measurements, revealing non-zero relaxation rates at zero temperature indicative of quantum effects.

Contribution

It introduces a quantum correction model for magnetic relaxation rates, demonstrating quantum tunneling in MgB$_2$ and how the energy barrier varies with temperature.

Findings

Quantum tunneling occurs in MgB$_2$ at low temperatures.

Relaxation rates do not approach zero at T=0 K.

The energy barrier $U_0$ increases as temperature decreases.

Abstract

Magnetic relaxation in a MgB$_2$ superconductor was measured. The temperature dependence of the normalized relaxation rate was determined for three different magnetic fields. By extrapolating these rates to T=0 K, we find that these extrapolations do not approach zero, indicating quantum tunneling of vortices in the superconductor. A quantum correction of the relaxation rate, followed by the correction of the magnetic moment, is proposed. Using the quantum correction, we find that $U_0$ increases with decreasing temperature and approaches a maximum at T=0.