Determination of the time scale of photoemission from the measurement of spin polarization

TL;DR

This paper reviews an analytical model linking spin polarization measurements to the Eisenbud-Wigner-Smith time delay in photoemission, providing improved bounds for time delays in copper surfaces.

Contribution

It introduces a distinction between scattering and interfering EWS time delays and applies the model to experimental data for better estimates.

Findings

Enhanced bounds for EWS time delays in Cu(111)

Clarification of interference effects on spin polarization

Application of model to recent experimental data

Abstract

The Eisenbud-Wigner-Smith (EWS) time delay of photoemission depends on the phase term of the matrix element describing the transition. Because of an interference process between partial channels, the photoelectrons acquire a spin polarization which is also related to the phase term. The analytical model for estimating the time delay by measuring the spin polarization is reviewed in this manuscript. In particular, the distinction between scattering EWS and interfering EWS time delay will be introduced, providing an insight in the chronoscopy of photoemission. The method is applied to the recent experimental data for Cu(111) presented in M. Fanciulli et al., PRL 118, 067402 (2017), allowing to give better upper and lower bounds and estimates for the EWS time delays.