Quantum Tunneling of the Magnetic Moment in the S/F/S Josephson ${\bm \varphi}_{\bf 0}$-Junction

TL;DR

This paper demonstrates that S/F/S Josephson $oldsymbol{}_0$-junctions can be used to detect macroscopic quantum tunneling and oscillations of magnetic moments through ac voltage measurements, with tunneling rates controllable by supercurrent.

Contribution

It provides an exact expression for tunnel splitting in $oldsymbol{}_0$-junctions and explores how magnetic tunneling can be controlled without magnetic fields.

Findings

Magnetic tunneling can be detected via ac voltage measurements.

Tunneling rate can be controlled by supercurrent, not magnetic field.

Magnetic tunneling may become frozen at large $oldsymbol{}_0$.

Abstract

We show that the S/F/S Josephson $\varphi_0$-junction permits detection of macroscopic quantum tunneling and quantum oscillation of the magnetic moment by measuring the ac voltage across the junction. Exact expression for the tunnel splitting renormalized by the interaction with the superconducting order parameter is obtained. It is demonstrated that magnetic tunneling may become frozen at a sufficiently large $\varphi_0$. The quality factor of quantum oscillations of the magnetic moment due to finite Ohmic resistance of the junction is computed. It is shown that magnetic tunneling rate in the $\varphi_0$-junction can be controled by the supercurrent, with no need for the magnetic field.