Spin Polarization and Attosecond Time Delay in Photoemission from Spin Degenerate States of Solids

After photon absorption, electrons from a dispersive band of a solid require a finite time in the photoemission process before being photoemitted as free particles, in line with recent attosecond-resolved photoemission experiments. According to the Eisenbud-Wigner-Smith model, the time delay is due to a phase shift of different transitions that occur in the process. Such a phase shift is also at the origin of the angular dependent spin polarization of the photoelectron beam, observable in spin degenerate systems without angular momentum transfer by the incident photon. We propose a semiquantitative model which permits us to relate spin and time scales in photoemission from condensed matter targets and to better understand spin-and angle-resolved photoemission spectroscopy (SARPES) experiments on spin degenerate systems. We also present the first experimental determination by SARPES of this time delay in a dispersive band, which is found to be greater than 26 as for electrons emitted from the sp-bulk band of the model system Cu(111).


Published in:
Physical Review Letters, 118, 6, 067402
Year:
2017
Publisher:
College Pk, American Physical Society
ISSN:
0031-9007
Note:
See also press release at: https://actu.epfl.ch/news/measuring-time-without-a-clock-2/
Laboratories:




 Record created 2017-03-27, last modified 2018-01-28

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