Rotational Quantum Tunneling of a Magnetic Dipole in a Superconducting Trap

TL;DR

This paper investigates the quantum rotational tunneling of a nano-magnet in a superconducting trap, highlighting decoherence effects and conditions for observable tunneling.

Contribution

It introduces a model for rotational quantum tunneling of a magnetic dipole in a superconducting trap and identifies symmetry conditions that protect tunneling from decoherence.

Findings

Rest-gas scattering is the main decoherence at low temperatures.

Near-perfect rotational symmetry can protect tunneling.

Feasible parameters for observing tunneling are identified.

Abstract

We study the quantum dynamics of the rotational degree of freedom of a nano-magnet trapped in a superconducting trap. The nano-magnet is modeled as a magnetic dipole with magnetization pinned to the easy axis of the particle. The magnetic trap then leads to a potential barrier that hinders free rotation of the particle, but through which it can tunnel. We identified rest-gas scattering as the most important decoherence mechanism at low temperatures. A shape of the particle sufficiently close to perfect rotational symmetry about the rotational axis can protect the rotational tunneling against this decoherence mechanism, and we identify experimentally feasible parameter regimes where rotational tunneling should be observable.