Non-linear THz-THG measurements reveal the interplay of Higgs modes and CDWs

Non-linear THz spectroscopy on the superconductor NbSe₂ in the framework of Higgs Spectroscopy shown an interplay of the superconducting Higgs mode and a charge density wave mode. Both modes contribute to a characteristic third harmonic generation signal and reveal an interplay in their time-domain signal. In the frequency domain this results in an anti-resonance feature that can be understood in a generalized Fano-interference picture of coupled modes.

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.108.L100504