Bardasis-Schrieffer polaritons in excitonic insulators

摘要: Bardasis-Schrieffer modes in superconductors are fluctuations subdominant pairing channels, e.g., $d$-wave an $s$-wave superconductor. This Rapid Communication shows that these also generically occur excitonic insulators. In insulators, a $p$-wave mode exists below the gap energy, is optically active, and hybridizes strongly with photons to form polaritons, which observable both far-field near-field optical experiments.