Anomalous acoustoelectric effect induced by clapping modes in chiral superconductors

TL;DR

This paper demonstrates that clapping modes in chiral superconductors can couple with acoustic waves to produce a resonantly enhanced transverse acoustoelectric effect, serving as a signature of chiral superconductivity.

Contribution

It reveals the direct coupling of clapping modes to acoustic waves and predicts a resonant transverse acoustoelectric effect as evidence of chiral superconductivity.

Findings

Clapping modes couple to acoustic waves in chiral superconductors.

Resonant transverse acoustoelectric current occurs below the continuum threshold.

Resonance serves as a smoking-gun signature of chiral superconductivity.

Abstract

Clapping modes, which are relative amplitude and phase modes between two chiral components of Cooper pairs, are bosonic collective modes inherent to chiral superconductors. These modes behave as long-lived bosons with masses smaller than the threshold energy, $2|\Delta|$, for decay into unbound fermion pairs. Here, we clarify that the real/imaginary clapping modes in chiral superconductors directly couple to acoustic wave propagation when the weak particle-hole asymmetry of the normal state quasiparticle dispersion is taken into account. The clapping modes driven by an acoustic wave generate an alternating electric current, that is, the acoustoelectric effect in superconductors. Significantly, the clapping modes give rise to a transverse electric current. When the sound velocity is comparable to the Fermi velocity, as in heavy fermion compounds, the transverse current is resonantly enhanced at energy below the threshold for continuum excitations. This resonance provides a smoking-gun evidence of chiral superconductivity.