TY  - JOUR
A1  - Krivenkov, Maxim
A1  - Marchenko, Dimitry
A1  - Sánchez-Barriga, Jaime
A1  - Golias, Evangelos
A1  - Rader, Oliver
A1  - Varykhalov, Andrei
T1  - Origin of the band gap in Bi-intercalated graphene on Ir(111)
JF  - 2D Materials
N2  - Proximity to heavy sp-elements is considered promising for reaching a band gap in graphene that could host quantum spin Hall states. The recent report of an induced spin-orbit gap of 0.2 eV in Pb-intercalated graphene detectable by spin-resolved photoemission has spurred renewed interest in such systems (Klimovskikh et al 2017 ACS Nano 11, 368). In the case of Bi intercalation an even larger band gap of 0.4 eV has been observed but was assigned to the influence of a dislocation network (Warmuth et al 2016 Phys. Rev. B 93, 165 437). Here, we study Bi intercalation under graphene on Ir(111) and report a nearly ideal graphene dispersion without band replicas and no indication of hybridization with the substrate. The band gap is small (0.19 eV) and can be tuned by +/- 25 meV through the Bi coverage. The Bi atomic density is higher than in the recent report. By spin-resolved photoemission we exclude induced spin-orbit interaction as origin of the gap. Quantitative agreement of a photoemission intensity analysis with the measured band gap suggests sublattice symmetry breaking as one of the possible band gap opening mechanisms. We test several Bi structures by density functional theory. Our results indicate the possibility that Bi intercalates in the phase of bismuthene forming a graphene-bismuthene van der Waals heterostructure.
KW  - graphene
KW  - bismuth
KW  - Ir(111)
KW  - spin-orbit interaction
KW  - ARPES
KW  - STM
KW  - bismuthene
Y1  - 2021
U6  - https://doi.org/10.1088/2053-1583/abd1e4
SN  - 2053-1583
VL  - 8
IS  - 3
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Utecht, Manuel Martin
A1  - Klamroth, Tillmann
T1  - Local resonances in STM manipulation of chlorobenzene on Si(111)-7x7
BT  - performance of different cluster models and density functionals
JF  - Molecular physics
N2  - Hot localised charge carriers on the Si(111)-7x7 surface are modelled by small charged clusters. Such resonances induce non-local desorption, i.e. more than 10 nm away from the injection site, of chlorobenzene in scanning tunnelling microscope experiments. We used such a cluster model to characterise resonance localisation and vibrational activation for positive and negative resonances recently. In this work, we investigate to which extent the model depends on details of the used cluster or quantum chemistry methods and try to identify the smallest possible cluster suitable for a description of the neutral surface and the ion resonances. Furthermore, a detailed analysis for different chemisorption orientations is performed. While some properties, as estimates of the resonance energy or absolute values for atomic changes, show such a dependency, the main findings are very robust with respect to changes in the model and/or the chemisorption geometry. [GRAPHICS] .
KW  - DFT
KW  - cluster model
KW  - charge localisation
KW  - STM
Y1  - 2018
U6  - https://doi.org/10.1080/00268976.2018.1442939
SN  - 0026-8976
SN  - 1362-3028
VL  - 116
IS  - 13
SP  - 1687
EP  - 1696
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Krivenkov, Maxim
A1  - Golias, Evangelos
A1  - Marchenko, Dmitry
A1  - Sanchez-Barriga, Jaime
A1  - Bihlmayer, Gustav
A1  - Rader, Oliver
A1  - Varykhalov, Andrei
T1  - Nanostructural origin of giant Rashba effect in intercalated graphene
JF  - 2D Materials
N2  - To enhance the spin-orbit interaction in graphene by a proximity effect without compromising the quasi-free-standing dispersion of the Dirac cones means balancing the opposing demands for strong and weak graphene-substrate interaction. So far, only the intercalation of Au under graphene/Ni(111) has proven successful, which was unexpected since graphene prefers a large separation (similar to 3.3 angstrom) from a Au monolayer in equilibrium. Here, we investigate this system and find the solution in a nanoscale effect. We reveal that the Au largely intercalates as nanoclusters. Our density functional theory calculations show that the graphene is periodically stapled to the Ni substrate, and this attraction presses graphene and Au nanoclusters together. This, in turn, causes a Rashba effect of the giant magnitude observed in experiment. Our findings show that nanopatterning of the substrate can be efficiently used for engineering of spin-orbit effects in graphene.
KW  - quasi-free-standing graphene
KW  - Ni(111)
KW  - gold intercalation
KW  - spin-orbit interaction
KW  - nanoclusters
KW  - STM
KW  - DFT
Y1  - 2017
U6  - https://doi.org/10.1088/2053-1583/aa7ad8
SN  - 2053-1583
VL  - 4
IS  - 3
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -