Experimental time-resolved photoemission and ab initio study of lifetimes of excited electrons in Mo and Rh

TL;DR

This study combines experimental time-resolved photoemission and ab initio calculations to analyze the excited electron lifetimes in molybdenum and rhodium, revealing the impact of 4d band occupation on relaxation dynamics.

Contribution

It provides a combined experimental and theoretical analysis of electron relaxation in Mo and Rh, highlighting the role of 4d band occupation in lifetime differences.

Findings

Theoretical approaches qualitatively match experimental trends.

GW+T calculations quantitatively agree with experiments for excitation energies >1 eV.

Increased 4d band occupation shortens excited electron lifetimes.

Abstract

We have studied the relaxation dynamics of optically excited electrons in molybdenum and rhodium by means of time resolved two-photon photoemission spectroscopy (TR-2PPE) and ab initio electron self-energy calculations performed within the GW and GW+T approximations. Both theoretical approaches reproduce qualitatively the experimentally observed trends and differences in the lifetimes of excited electrons in molybdenum and rhodium. For excitation energies exceeding the Fermi energy by more than 1 eV, the GW+T theory yields lifetimes in quantitative agreement with the experimental results. As one of the relevant mechanisms causing different excited state lifetime in Mo and Rh we identify the occupation of the 4d bands. An increasing occupation of the 4d bands results in an efficient decrease of the lifetime even for rather small excitation energies of a few 100 meV.