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.

References in corpus (13)

• Amplitude / Higgs Modes in Condensed Matter Physics
• The `Higgs' Amplitude Mode at the Two-Dimensional Superfluid-Mott Insulator Transition
• Quantum Fluctuations in the Superfluid State of the BCS-BEC Crossover
• The Higgs mode in a two-dimensional superfluid
• Higgs mode in a strongly interacting fermionic superfluid
• Amplitude Higgs mode and admittance in superconductors with a moving condensate
• Nature and Raman signatures of the Higgs amplitude mode in the coexisting superconducting and charge-density-wave state
• Direct observation of the Higgs amplitude mode in a two-dimensional quantum antiferromagnet near the quantum critical point
• Higgs amplitude mode in the vicinity of a $(2+1)$-dimensional quantum critical point: a nonperturbative renormalization-group approach
• Universal Properties of the Higgs Resonance in (2+1)-Dimensional U(1) Critical Systems
• Spectral function of the Higgs mode in 4-\varepsilon dimensions
• Dynamical structure factors of a two-dimensional Fermi superfluid within random phase approximation
• Dynamic properties of superconductors: Anderson-Bogoliubov mode and Berry phase in BCS and BEC regimes