Following the Higgs mode across the BCS-BEC crossover in two dimensions

Abstract

Although substantial effort has been dedicated to analyzing the Higgs (amplitude) mode in superconducting systems, there are relatively few studies of the Higgs peak's dispersion and width, quantities which are observable in spectroscopic measurements. These properties can be obtained from the location of the pole of the longitudinal (Higgs) susceptibility in the lower half-plane of complex frequency. We analyze the behavior of the Higgs mode in a 2D neutral fermionic superfluid at $T=0$ throughout the crossover from Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensation (BEC) behavior. This occurs when the dressed chemical potential $\mu$ changes sign from positive to negative. For $\mu >0$, we find a pole in the Higgs susceptibility in the lower half-plane of frequency and demonstrate that it leads to a well-defined peak in spectroscopic probes. For $\mu <0$, the pole still exists, but is "hidden," not giving rise to a peak in spectroscopic probes. Extending this analysis to a charged superconductor, we find that the Higgs mode is unaffected by the long-range Coulomb interaction.

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Cited by in corpus (8)

• Nonlinear Response of Diffusive Superconductors to $ac$-electromagnetic Fields
• The Condensation of Ideal Dunkl-Bose Gas in Power-Law Traps
• Spatially-resolved dynamics of the amplitude Schmid-Higgs mode in disordered superconductors
• Dynamic structure factor of two-dimensional Fermi superfluid with Rashba spin-orbit coupling
• Quantum Fluctuations and Multifractally-Enhanced Superconductivity in Disordered Thin Films
• Spectrum of density, spin and pairing fluctuations of an attractive two-dimensional Fermi gas
• Spatially resolved collective modes in d-wave superconductors
• AC Josephson Signatures of the Superconducting Higgs Mode