TY  - JOUR
A1  - Stühler, R.
A1  - Kowalewski, A.
A1  - Reis, F.
A1  - Jungblut, D.
A1  - Dominguez, F.
A1  - Scharf, B.
A1  - Li, G.
A1  - Schäfer, J.
A1  - Hankiewicz, E. M.
A1  - Claessen, R.
T1  - Effective lifting of the topological protection of quantum spin Hall edge states by edge coupling
JF  - Nature Communications
N2  - The scientific interest in two-dimensional topological insulators (2D TIs) is currently shifting from a more fundamental perspective to the exploration and design of novel functionalities. Key concepts for the use of 2D TIs in spintronics are based on the topological protection and spin-momentum locking of their helical edge states. In this study we present experimental evidence that topological protection can be (partially) lifted by pairwise coupling of 2D TI edges in close proximity. Using direct wave function mapping via scanning tunneling microscopy/spectroscopy (STM/STS) we compare isolated and coupled topological edges in the 2D TI bismuthene. The latter situation is realized by natural lattice line defects and reveals distinct quasi-particle interference (QPI) patterns, identified as electronic Fabry-Pérot resonator modes. In contrast, free edges show no sign of any single-particle backscattering. These results pave the way for novel device concepts based on active control of topological protection through inter-edge hybridization for, e.g., electronic Fabry-Pérot interferometry.
KW  - topological insulators
KW  - two-dimensional materials
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300886
VL  - 13
ER  - 
TY  - JOUR
A1  - Lundt, Nils
A1  - Klembt, Sebastian
A1  - Cherotchenko, Evgeniia
A1  - Betzold, Simon
A1  - Iff, Oliver
A1  - Nalitov, Anton V.
A1  - Klaas, Martin
A1  - Dietrich, Christof P.
A1  - Kavokin, Alexey V.
A1  - Höfling, Sven
A1  - Schneider, Christian
T1  - Room-temperature Tamm-plasmon exciton-polaritons with a WSe\(_{2}\) monolayer
JF  - Nature Communications
N2  - Solid-state cavity quantum electrodynamics is a rapidly advancing field, which explores the frontiers of light–matter coupling. Metal-based approaches are of particular interest in this field, as they carry the potential to squeeze optical modes to spaces significantly below the diffraction limit. Transition metal dichalcogenides are ideally suited as the active material in cavity quantum electrodynamics, as they interact strongly with light at the ultimate monolayer limit. Here, we implement a Tamm-plasmon-polariton structure and study the coupling to a monolayer of WSe\(_{2}\), hosting highly stable excitons. Exciton-polariton formation at room temperature is manifested in the characteristic energy–momentum dispersion relation studied in photoluminescence, featuring an anti-crossing between the exciton and photon modes with a Rabi-splitting of 23.5 meV. Creating polaritonic quasiparticles in monolithic, compact architectures with atomic monolayers under ambient conditions is a crucial step towards the exploration of nonlinearities, macroscopic coherence and advanced spinor physics with novel, low-mass bosons.
KW  - optics and photonics
KW  - two-dimensional materials
KW  - electronic properties and materials
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-169470
VL  - 7
ER  - 
TY  - JOUR
A1  - Shamim, Saquib
A1  - Mahapatra, S.
A1  - Scappucci, G.
A1  - Klesse, W. M.
A1  - Simmons, M. Y.
A1  - Ghosh, Arindam
T1  - Dephasing rates for weak localization and universal conductance fluctuations in two dimensional Si: P and Ge: P δ-layers
JF  - Scientific Reports
N2  - We report quantum transport measurements on two dimensional (2D) Si:P and Ge:P δ-layers and compare the inelastic scattering rates relevant for weak localization (WL) and universal conductance fluctuations (UCF) for devices of various doping densities (0.3–2.5 × 10\(^{18}\)m\(^{−2}\)) at low temperatures (0.3–4.2 K). The phase breaking rate extracted experimentally from measurements of WL correction to conductivity and UCF agree well with each other within the entire temperature range. This establishes that WL and UCF, being the outcome of quantum interference phenomena, are governed by the same dephasing rate.
KW  - two-dimensional materials
KW  - quantum information
KW  - electronic properties and materials
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170934
VL  - 7
IS  - 46670
ER  - 
TY  - JOUR
A1  - Wurdack, Matthias
A1  - Lundt, Nils
A1  - Klaas, Martin
A1  - Baumann, Vasilij
A1  - Kavokin, Alexey V.
A1  - Höfling, Sven
A1  - Schneider, Christian
T1  - Observation of hybrid Tamm-plasmon exciton-polaritons with GaAs quantum wells and a MoSe\(_{2}\) monolayer
JF  - Nature Communications
N2  - Strong light matter coupling between excitons and microcavity photons, as described in the framework of cavity quantum electrodynamics, leads to the hybridization of light and matter excitations. The regime of collective strong coupling arises, when various excitations from different host media are strongly coupled to the same optical resonance. This leads to a well-controllable admixture of various matter components in three hybrid polariton modes. Here, we study a cavity device with four embedded GaAs quantum wells hosting excitons that are spectrally matched to the A-valley exciton resonance of a MoSe\(_{2}\) monolayer. The formation of hybrid polariton modes is evidenced in momentum resolved photoluminescence and reflectivity studies. We describe the energy and k-vector distribution of exciton-polaritons along the hybrid modes by a thermodynamic model, which yields a very good agreement with the experiment.
KW  - two-dimensional materials
KW  - microresonators
KW  - nanophotonics and plasmonics
KW  - cavity device
KW  - strong coupling
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170480
VL  - 8
IS  - 259
ER  -