Superconducting collective Leggett modes in single-layer 1H-NbSe2

The superconducting state of single-layer 1H-NbSe2 has recently been shown to display several surprising features, including our report of the existence of a bosonic mode intrinsic to the superconducting state seen as a set of resonances in tunneling spectra, which show a clear anticorrelation with the superconducting gap. We have argued that these resonances can be interpreted as a Leggett-like superconducting collective mode associated to a subleading f-wave triplet channel. In this talk, I will present a calculation of the Leggett mode energy using a simplified continuum model for NbSe2. I will discuss how our model compares with the experimental data, discuss the origin of the anticorrelation, and argue that it provides support to the competing pairing scenario, with a sizable attraction in the subleading triplet channel.