Collective modes and terahertz near-field response of superconductors

  title={Collective modes and terahertz near-field response of superconductors},
  author={Zhiyuan Sun and Michael M. Fogler and Dimitri Basov and Andrew J. Millis},
  journal={arXiv: Superconductivity},
We theoretically study the low energy electromagnetic response of BCS type superconductors focusing on propagating collective modes that are observable with THz near field optics. The interesting frequency and momentum range is $\omega < 2\Delta$ and $q < 1/\xi$ where $\Delta$ is the gap and $\xi$ is the coherence length. We show that it is possible to observe the superfluid plasmons, amplitude (Higgs) modes, Bardasis-Schrieffer modes and Carlson-Goldman modes using THz near field technique… 

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