Reducing the frequency of the Higgs mode in a helical superconductor coupled to an LC-circuit

TL;DR

This paper demonstrates that coupling a helical superconductor with strong spin-orbit interaction to an LC circuit enables the detection of the Higgs mode at lower frequencies, facilitating experimental observation via microwave spectroscopy.

Contribution

It introduces a method to couple the Higgs mode in a superconductor to an electromagnetic circuit, making it observable at accessible frequencies.

Findings

Higgs mode couples linearly to electromagnetic fields in such superconductors.

Coupling to an LC circuit shifts the Higgs resonance to lower, detectable frequencies.

Proposes microwave spectroscopy as a method for Higgs mode detection.

Abstract

We show that the amplitude, or Higgs mode of a superconductor with strong spin-orbit coupling and an exchange field, couples linearly to the electromagnetic field. Furthermore, by coupling such a superconductor to an LC resonator, we demonstrate that the Higgs resonance becomes a regular mode at frequencies smaller than the quasiparticle energy threshold $2\Delta$. We finally propose and discuss a possible experiment based on microwave spectroscopy for an unequivocal detection of the Higgs mode. Our approach may allow visualizing Higgs modes also in more complicated multiband superconductors with a coupling between the charge and other electronic degrees of freedom.