Energy dissipation from a correlated system driven out of equilibrium.

J D Rameau,J K Freericks,I Avigo,G D Gu,R D Zhong,Y Yoshida,M A Sentef,L Rettig,U Bovensiepen,J Schneeloch,Z J Xu,S Freutel,P D Johnson,M Ligges,H Eisaki,A F Kemper

doi:10.1038/ncomms13761

Abstract

In complex materials various interactions have important roles in determining electronic properties. Angle-resolved photoelectron spectroscopy (ARPES) is used to study these processes by resolving the complex single-particle self-energy and quantifying how quantum interactions modify bare electronic states. However, ambiguities in the measurement of the real part of the self-energy and an intrinsic inability to disentangle various contributions to the imaginary part of the self-energy can leave the implications of such measurements open to debate. Here we employ a combined theoretical and experimental treatment of femtosecond time-resolved ARPES (tr-ARPES) show how population dynamics measured using tr-ARPES can be used to separate electron–boson interactions from electron–electron interactions. We demonstrate a quantitative analysis of a well-defined electron–boson interaction in the unoccupied spectrum of the cuprate Bi2Sr2CaCu2O8+x characterized by an excited population decay time that maps directly to a discrete component of the equilibrium self-energy not readily isolated by static ARPES experiments.

Highlights

In complex materials various interactions have important roles in determining electronic properties
Employing nonequilibrium Green’s functions theory, we demonstrate how to make quantitative conclusions based on these observations, and show that the e–p coupling leaves its mode-specific fingerprint on the population dynamics
Using tr-Angle-resolved photoelectron spectroscopy (ARPES), we observe population relaxation dynamics, which we describe by interaction with a specific phonon after excitation by a light field

Summary

Introduction

In complex materials various interactions have important roles in determining electronic properties. This superposition of single-particle selfenergies complicates the disentanglement of the individual interactions, which is desirable to be able to understand the electron–boson (e–b) and electron–electron (e–e) interactions Quasiparticle lifetimes and their related mass renormalizations can in some cases be directly measured using angle-resolved photoemission spectroscopy (ARPES) by studying the linewidth G(E) or effective dispersion E(k), obtaining the imaginary or real parts of the self-energy (ImS(E) and ReS(E)), respectively[1,2,3,4,5,6]. The lifetime analysis of the laser-excited population relaxation by kinetic rate equations or density matrix formalism[7,13] has proven successful for quasiparticle energies between B0.5 to several eV in a limit where relaxation is dominant at all times and quasiparticle lifetimes can be determined in the time domain[7,14,15,16]

Methods

Results

Conclusion