SmB6electron-phonon coupling constant from time- and angle-resolved photoelectron spectroscopy

Abstract

${\mathrm{SmB}}_{6}$ is a mixed valence Kondo system resulting from the hybridization between localized $f$ electrons and delocalized $d$ electrons. We have investigated its out-of-equilibrium electron dynamics by means of time- and angle-resolved photoelectron spectroscopy. The transient electronic population above the Fermi level can be described by a time-dependent Fermi-Dirac distribution. By solving a two-temperature model that well reproduces the relaxation dynamics of the effective electronic temperature, we estimate the electron-phonon coupling constant $\ensuremath{\lambda}$ to range from $0.13\ifmmode\pm\else\textpm\fi{}0.03$ to $0.04\ifmmode\pm\else\textpm\fi{}0.01$. These extremes are obtained assuming a coupling of the electrons with either a phonon mode at 10 or 19 meV. A realistic value of the average phonon energy will give an actual value of $\ensuremath{\lambda}$ within this range. Our results provide an experimental report on the material electron-phonon coupling, contributing to both the electronic transport and the macroscopic thermodynamic properties of ${\mathrm{SmB}}_{6}$.