Interaction of a Nanomagnet with a Weak Superconducting Link

TL;DR

This paper investigates the electromagnetic interaction between a nanomagnet and a weak superconducting link, revealing how magnetic dynamics can be detected and manipulated through electrical signals and quantum effects.

Contribution

It derives coupled dynamical equations and explores both classical and quantum behaviors of the nanomagnet-superconductor system, highlighting new detection and control mechanisms.

Findings

Detection of nanomagnet presence via Shapiro-like steps.

Voltage-induced reversal of nanomagnet's magnetic moment.

Quantum tunneling effects in the spin states of the nanomagnet.

Abstract

We study electromagnetic interaction of a nanomagnet with a weak superconducting link. Equations that govern coupled dynamics of the two systems are derived and investigated numerically. We show that the presence of a small magnet in the proximity of a weak link may be detected through Shapiro-like steps caused by the precession of the magnetic moment. Despite very weak magnetic field generated by the weak link, a time-dependent bias voltage applied to the link can initiate a non-linear dynamics of the nanomagnet that leads to the reversal of its magnetic moment. We also consider quantum problem in which a nanomagnet interacting with a weak link is treated as a two-state spin system due to quantum tunneling between spin-up and spin-down states.