Nonreciprocal Terahertz Second Harmonic Generation in Superconducting NbN under Supercurrent Injection

Sachiko Nakamura, Kota Katsumi, Hirotaka Terai +1

Giant second-harmonic generation (SHG) in the terahertz (THz) frequency range is observed in a thin film of an s-wave superconductor NbN, where the time-reversal ($\mathcal{T}$-) a…