Energy dissipation from a correlated material driven out of equilibrium

Rameau JD, Freutel S, Kemper AF, Sentef MA, Yoshida Y, Eisaki H, Freericks JK, Avigo I, Ligges M, Rettig L, Schneeloch J, Zhong RD, Xu ZJ, Gu GD, Johnson PD, Bovensiepen U
Nature Communications 7, 13761 (2016)

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.