TY  - JOUR
A1  - Clark, Oliver J.
A1  - Freyse, Friedrich
A1  - Yashina, L. V.
A1  - Rader, Oliver
A1  - Sanchez-Barriga, Jaime
T1  - Robust behavior and spin-texture stability of the topological surface state in Bi2Se3 upon deposition of gold
JF  - npj quantum materials
N2  - The Dirac point of a topological surface state (TSS) is protected against gapping by time-reversal symmetry. Conventional wisdom stipulates, therefore, that only through magnetisation may a TSS become gapped. However, non-magnetic gaps have now been demonstrated in Bi2Se3 systems doped with Mn or In, explained by hybridisation of the Dirac cone with induced impurity resonances. Recent photoemission experiments suggest that an analogous mechanism applies even when Bi2Se3 is surface dosed with Au. Here, we perform a systematic spin- and angle-resolved photoemission study of Au-dosed Bi2Se3. Although there are experimental conditions wherein the TSS appears gapped due to unfavourable photoemission matrix elements, our photon-energy-dependent spectra unambiguously demonstrate the robustness of the Dirac cone against high Au coverage. We further show how the spin textures of the TSS and its accompanying surface resonances remain qualitatively unchanged following Au deposition, and discuss the mechanism underlying the suppression of the spectral weight.
KW  - Electronic properties and materials
KW  - Topological matter
Y1  - 2022
U6  - https://doi.org/10.1038/s41535-022-00443-9
SN  - 2397-4648
VL  - 7
IS  - 1
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - GEN
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
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
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.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1354 
KW  - AG
KW  - films
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-549892
SN  - 1866-8372
IS  - 1
ER  - 
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  -