Higgs mode stabilization by photo-induced long-range interactions in a superconductor

TL;DR

This paper demonstrates that coupling a 2D BCS superconductor to a driven cavity induces long-range interactions that stabilize the Higgs mode by pushing it below the quasiparticle continuum, enhancing its lifetime.

Contribution

It introduces a method to stabilize the Higgs mode in superconductors through photo-induced long-range interactions, a novel approach in superconductor control.

Findings

Higgs mode is pushed into the gap, below quasiparticle continuum.

Long-range cavity-induced interactions enlarge the superconducting gap.

Additional collective excitations emerge due to long-range interactions.

Abstract

We show that low-lying excitations of a 2D BCS superconductor are significantly altered when coupled to an externally driven cavity, which induces controllable long-range attractive interactions between the electrons. We find that they combine non-linearly with intrinsic local interactions to increase the Bogoliubov quasiparticle excitation energies, thus enlarging the superconducting gap. The long-range nature of the driven-cavity-induced attraction qualitatively changes the collective excitations of the superconductor. Specifically, they lead to the appearance of additional collective excitations of the excitonic modes. Furthermore, the Higgs mode is pushed into the gap and now lies below the Bogoliubov quasiparticle continuum such that it cannot decay into quasiparticles. This way, the Higgs mode's lifetime is greatly enhanced.