Spectroscopic fingerprints of many-body renormalizations in$1T$-TiSe$_2$

TL;DR

This study uses high-resolution ARPES to identify many-body interactions in $1T$-TiSe$_2$, revealing multiple kink structures and electron-phonon coupling signatures linked to charge density wave and superconductivity phenomena.

Contribution

It provides the first direct observation of multiple kink structures and identifies specific Bosonic modes involved in electron-phonon interactions in $1T$-TiSe$_2$.

Findings

Identification of multiple kink structures in electronic dispersion.

Detection of Bosonic modes at ~15 and 26 meV.

Implication of electron-phonon coupling in collective states.

Abstract

We have employed high resolution angle resolved photoemission spectroscopy (ARPES) measurements to investigate many-body renormalizations of the single-particle excitations in $1T$-TiSe$_2$. The energy distribution curves of the ARPES data reveal intrinsic peak-dip-hump feature, while the electronic dispersion derived from the momentum distribution curves of the data highlights, for the first time, multiple kink structures. These are canonical signatures of a coupling between the electronic degrees of freedom and some Bosonic mode in the system. We demonstrate this using a model calculation of the single-particle spectral function at the presence of an electron-Boson coupling. From the self-energy analysis of our ARPES data, we discern some of the critical energy scales of the involved Bosonic mode, which are $\sim$15 and 26 meV. Based on a comparison between these energies and the characteristic energy scales of our Raman scattering data, we identify these Bosonic modes as Raman active breathing (${\text{A}}_\text{1g}$) and shear (${\text{E}}_\text{g}$) modes, respectively. Direct observation of the band-renormalization due to electron-phonon coupling increases the possibility that electron-phonon interactions are central to the collective quantum states such as charge density wave (CDW) and superconductivity in the compounds based on $1T$-TiSe$_2$.