Spectroscopic fingerprints of many-body renormalization in 1T-TiSe2

Abstract

We have investigated many-body renormalizations of the single-particle excitations in 1T-TiSe2 by employing high resolution angle-resolved photoemission spectroscopy (ARPES) measurements. The energy distribution curves (EDCs) of the ARPES data reveal an intrinsic single band peak-dip-hump (PDH) feature. Furthermore, the renormalized electronic dispersion extracted from the momentum distribution curves (MDCs) highlights a well-defined kink structure. These are canonical signatures of many-body correlations in the system. Theoretical modeling of the electrons coupled to an Einstein mode illustrates that a study of the renormalized dispersion from the MDCs enable direct access to the characteristic features of these many-body correlations, such as the energy scale of the relevant collective mode and the strength of its coupling with the electrons in the system. This model also demonstrates the difficulty to determine these features in a straightforward way from the PDH structure of the EDCs. The self-energy analysis of our ARPES data suggest compelling evidence for a bosonic mode having energy ∼26meV, with which the electrons in 1T-TiSe2 couple to. This correlates with the ab initio phonon-dispersion calculations and the observation of breathing (A1g) phonon mode in Raman scattering experiments.