Abstract
Recent studies have emphasized the importance of impurity scattering for the optical Higgs response of superconductors. In the dirty limit, an additional paramagnetic coupling of light to the superconducting condensate arises which drastically enhances excitation. So far, most work concentrated on the periodic driving with light, where the third-harmonic generation response of the Higgs mode was shown to be enhanced. In this work, we additionally calculate the time-resolved optical conductivity of single- and two-band superconductors in a two-pulse quench-probe setup, where we find good agreement with existing experimental results. We use the Mattis-Bardeen approach to incorporate impurity scattering and calculate explicitly the time-evolution of the system. Calculations are performed both in a diagrammatic picture derived from an effective action formalism and within a time-dependent density matrix formalism.
Highlights
When a continuous symmetry is spontaneously broken, collective excitations emerge
Most work concentrated on the periodic driving with light, where the third-harmonic generation (THG) response of the Higgs mode was shown to be enhanced
We extend this analysis by calculating full temperature and frequency dependence of THG to better compare the theory with current experimental setups
Summary
When a continuous symmetry is spontaneously broken, collective excitations emerge. In the case of a superconductor, where the complex order parameter eiθ acquires a finite value below a critical temperature TC, two bosonic modes appear: the massive Higgs mode and a massless Goldstone mode [1,2]. Our results support the findings of a recent paper, where the third-harmonic response in the two-band superconductor MgB2 shows a resonance only for the lower gap [17] This can be understood from the fact that the upper band is either in the clean limit or that the Fermi surface is very small. In addition to the investigations of previous work on the effect of impurities in the periodic driving scheme, in this paper, we explore the excitation with a two-pulse quench-probe scheme We consider both one- and two-band superconductors where the bands can be in different impurity regimes. We incorporate the effect of impurities in our model using the Mattis-Bardeen approximation [24] This approach constitutes an excellent description for many conventional superconductors at least in the linear regime [25].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
