TY  - JOUR
A1  - Varykhalov, Andrei
A1  - Freyse, Friedrich
A1  - Aguilera, Irene
A1  - Battiato, Marco
A1  - Krivenkov, Maxim
A1  - Marchenko, Dmitry
A1  - Bihlmayer, Gustav
A1  - Blugel, Stefan
A1  - Rader, Oliver
A1  - Sanchez-Barriga, Jaime
T1  - Effective mass enhancement and ultrafast electron dynamics of Au(111) surface state coupled to a quantum well
JF  - Physical Review Research
N2  - We show that, although the equilibrium band dispersion of the Shockley-type surface state of two-dimensional Au(111) quantum films grown on W(110) does not deviate from the expected free-electron-like behavior, its nonequilibrium energy-momentum dispersion probed by time- and angle-resolved photoemission exhibits a remarkable kink above the Fermi level due to a significant enhancement of the effective mass. The kink is pronounced for certain thicknesses of the Au quantum well and vanishes in the very thin limit. We identify the kink as induced by the coupling between the Au(111) surface state and emergent quantum-well states which probe directly the buried gold-tungsten interface. The signatures of the coupling are further revealed by our time-resolved measurements which show that surface state and quantum-well states thermalize together behaving as dynamically locked electron populations. In particular, relaxation of hot carriers following laser excitation is similar for both surface state and quantum-well states and much slower than expected for a bulk metallic system. The influence of quantum confinement on the interplay between elementary scattering processes of the electrons at the surface and ultrafast carrier transport in the direction perpendicular to the surface is shown to be the reason for the slow electron dynamics.
KW  - AG
KW  - Flims
Y1  - 2020
U6  - https://doi.org/10.1103/PhysRevResearch.2.013343
SN  - 0031-9007
VL  - 2
IS  - 1
SP  - 1
EP  - 9
PB  - American Physical Society
CY  - Ridge, NY
ER  -