Abstract
We examine the problem of how excited populations of electrons relax after they have been excited by a pump. We include three of the most important relaxation processes: (i) impurity scattering, (ii) Coulomb scattering, and (iii) electron-phonon scattering. The relaxation of an excited population of electrons is one of the most fundamental processes measured in pump-probe experiments, but its interpretation remains under debate. We show how several common assumptions about nonequilibrium relaxation that are pervasive in the field may not hold under quite general conditions. The analysis shows that nonequilibrium relaxation is more complex than previously thought, but it yields to recently developed theoretical methods in nonequilibrium theory. In this work, we show how one can use many-body theory to properly interpret and analyze these complex systems. We focus much of the discussion on implications of these results for experiment.
- Received 22 August 2017
- Revised 20 April 2018
DOI:https://doi.org/10.1103/PhysRevX.8.041009
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Nonequilibrium spectroscopy is rapidly gaining in popularity as a tool to study quantum materials. Up to now, interpretation of these experiments has commonly relied on intuition developed from equilibrium physics, even when the system of interest is driven far from equilibrium. Our work lays out the very common misconceptions that arise in doing so and proposes an alternative viewpoint upon which the experiments may be analyzed.
Specifically, we examine the problem of how excited populations of electrons relax after they have been excited by a pump. We include three of the most important relaxation processes: impurity scattering, Coulomb scattering, and electron-phonon scattering. Our analysis shows that nonequilibrium relaxation is more complex than previously thought, but it yields to recently developed theoretical methods in nonequilibrium theory. We show how one can use many-body theory to properly interpret and analyze these complex systems.
We will use the techniques and ideas developed here to go beyond the normal state and study the ordered phases of matter that emerge in condensed-matter systems.
