Collective Resonance of Superconducting/Normal Domain Walls in the Intermediate State of type-I superconductor

TL;DR

This study uses ac magnetostriction to reveal collective oscillations of superconducting/normal interfaces in lead's intermediate state, uncovering a new dynamical behavior not visible in traditional magnetic measurements.

Contribution

It demonstrates that ac magnetostriction can detect collective interface oscillations in type-I superconductors, revealing a fundamental dynamical channel.

Findings

Identified a quasiresonant response with sign reversal in the imaginary component.

Observed non-monotonic evolution of the real part with frequency.

Attributed the behavior to eddy current-driven collective oscillations of S/N interfaces.

Abstract

The dynamics of phase boundaries, such as superconducting/normal (S/N) interfaces in type-I superconductors, are typically obscured in conventional magnetic measurements, which are dominated by surface barriers and over-damped flux processes. Here, we employ ac magnetostriction as a sensitive probe to reveal the distinct bulk dynamics of these domain walls in the intermediate state of lead. In contrast to the Debye-type relaxation observed in magnetic susceptibility, we discover a pronounced quasiresonant response characterized by a sign reversal of the imaginary component and a non-monotonic evolution of the real part with frequency. We attribute this behavior to the collective oscillations of S/N interfaces driven by eddy currents generated within the normal domains. This work uncovers a fundamental dynamical channel in superconducting modulated phases and establishes ac magnetostrictive coefficient as a powerful tool for probing hidden interface physics.