NMR-like effect on Anisotropic Magnetic Moment of Surface Bound States in Topological Superfluid $^3$He-B

TL;DR

This paper reports the experimental observation of an NMR-like effect on surface-bound states in topological superfluid $^3$He-B, revealing a novel damping phenomenon linked to anisotropic magnetic moments at ultra-low temperatures.

Contribution

It introduces a new NMR-like effect induced by mechanical resonator motion on surface states in superfluid $^3$He-B, distinct from classical NMR methods.

Findings

Observation of maximum damping at Larmor resonance condition.

Identification of anisotropic magnetic moments near the surface.

Evidence of symmetry violation affecting surface states.

Abstract

We present experimental observation of a new phenomenon, that we interpret as NMR-like effect on anisotropic magnetic moment of the surface Andreev bound states in topological superfluid $^3$He-B at zero temperature limit. We show that an anisotropic magnetic moment formed near the horizontal surface of a mechanical resonator due to symmetry violation of the superfluid $^3$He-B order parameter by the resonator's surface may lead to anomalous damping of the resonator motion in magnetic field. In difference to classical NMR technique, here NMR was excited using own harmonic motion of the mechanical resonator, and nuclear magnetic resonance was detected as a maximum in damping when resonator's angular frequency satisfied the Larmor resonance condition.