Spectroscopic signature of the $\mathbf{k}$-dependent electron-phonon coupling in $2H$-TaS$_2$

TL;DR

This study uses ARPES to reveal momentum-dependent electron-phonon interactions in 2H-TaS2, showing persistent kink features above the CDW transition temperature and indicating a phononic origin of many-body effects.

Contribution

It provides the first detailed momentum-resolved evidence of k-dependent electron-phonon coupling in 2H-TaS2 through temperature-independent kink analysis.

Findings

Presence of multiple dispersion kinks indicating many-body effects

Kink energies are temperature-independent and persist above T_cdw

Detection of momentum-anisotropic electron-phonon coupling

Abstract

Our detailed Angle Resolved Photoemission Spectroscopy (ARPES) study of $2H$-TaS$_2$, a canonical incommensurate charge density wave (CDW) material, illustrates pronounced many-body renormalization in the system, which is manifested by the presence of multiple kink structures in the electronic dispersions. Temperature-dependent measurements reveal that these kink structures persist even at temperatures higher than the charge density wave transition temperature $\it{T}_{\text{cdw}}\,$ and the energy locations of the kinks are practically temperature-independent. Correlating kink energies with the published Raman scattering data and the theoretically calculated phonon spectrum of $2H$-TaS$_2$, we conclude phononic mechanism for these kinks. We have also detected momentum-anisotropy in the band renormalization, which in turn indicates momentum-dependence of the electron-phonon coupling of the system.