TY  - JOUR
A1  - Tuan, Dinh Van
A1  - Scharf, Benedikt
A1  - Žutič, Igor
A1  - Dery, Hanan
T1  - Marrying excitons and plasmons in monolayer transition-metal dichalcogenides
JF  - Physical Review X
N2  - Just as photons are the quanta of light, plasmons are the quanta of orchestrated charge-density oscillations in conducting media. Plasmon phenomena in normal metals, superconductors, and doped semiconductors are often driven by long-wavelength Coulomb interactions. However, in crystals whose Fermi surface is comprised of disconnected pockets in the Brillouin zone, collective electron excitations can also attain a shortwave component when electrons transition between these pockets. In this work, we show that the band structure of monolayer transition-metal dichalcogenides gives rise to an intriguing mechanism through which shortwave plasmons are paired up with excitons. The coupling elucidates the origin for the optical sideband that is observed repeatedly in monolayers of WSe\(_2\) and WS\(_2\) but not understood. The theory makes it clear why exciton-plasmon coupling has the right conditions to manifest itself distinctly only in the optical spectra of electron-doped tungsten-based monolayers.
KW  - physics
KW  - excitons
KW  - plasmons
KW  - semiconductors
KW  - spintronics
KW  - valleytronics
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-173030
VL  - 7
IS  - 4
ER  - 
TY  - JOUR
A1  - Suchomel, H.
A1  - Brodbeck, S.
A1  - Liew, T. C. H.
A1  - Amthor, M.
A1  - Klaas, M.
A1  - Klembt, S.
A1  - Kamp, M.
A1  - Höfling, S.
A1  - Schneider, C.
T1  - Prototype of a bistable polariton field-effect transistor switch
JF  - Scientific Reports
N2  - Microcavity exciton polaritons are promising candidates to build a new generation of highly nonlinear and integrated optoelectronic devices. Such devices range from novel coherent light emitters to reconfigurable potential landscapes for electro-optical polariton-lattice based quantum simulators as well as building blocks of optical logic architectures. Especially for the latter, the strongly interacting nature of the light-matter hybrid particles has been used to facilitate fast and efficient switching of light by light, something which is very hard to achieve with weakly interacting photons. We demonstrate here that polariton transistor switches can be fully integrated in electro-optical schemes by implementing a one-dimensional polariton channel which is operated by an electrical gate rather than by a control laser beam. The operation of the device, which is the polariton equivalent to a field-effect transistor, relies on combining electro-optical potential landscape engineering with local exciton ionization to control the scattering dynamics underneath the gate. We furthermore demonstrate that our device has a region of negative differential resistance and features a completely new way to create bistable behavior.
KW  - materials for optics
KW  - nanoscience and technology
KW  - optics and photonics
KW  - semiconductors
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-158323
VL  - 7
IS  - 5114
ER  - 
TY  - JOUR
A1  - Peixoto, Thiago R. F.
A1  - Bentmann, Hendrik
A1  - Rüßmann, Philipp
A1  - Tcakaev, Abdul-Vakhab
A1  - Winnerlein, Martin
A1  - Schreyeck, Steffen
A1  - Schatz, Sonja
A1  - Vidal, Raphael Crespo
A1  - Stier, Fabian
A1  - Zabolotnyy, Volodymyr
A1  - Green, Robert J.
A1  - Min, Chul Hee
A1  - Fornari, Celso I.
A1  - Maaß, Henriette
A1  - Vasili, Hari Babu
A1  - Gargiani, Pierluigi
A1  - Valvidares, Manuel
A1  - Barla, Alessandro
A1  - Buck, Jens
A1  - Hoesch, Moritz
A1  - Diekmann, Florian
A1  - Rohlf, Sebastian
A1  - Kalläne, Matthias
A1  - Rossnagel, Kai
A1  - Gould, Charles
A1  - Brunner, Karl
A1  - Blügel, Stefan
A1  - Hinkov, Vladimir
A1  - Molenkamp, Laurens W.
A1  - Friedrich, Reinert
T1  - Non-local effect of impurity states on the exchange coupling mechanism in magnetic topological insulators
JF  - NPJ Quantum Materials
N2  - Since the discovery of the quantum anomalous Hall (QAH) effect in the magnetically doped topological insulators (MTI) Cr:(Bi,Sb)\(_2\)Te\(_3\) and V:(Bi,Sb)\(_2\)Te\(_3\), the search for the magnetic coupling mechanisms underlying the onset of ferromagnetism has been a central issue, and a variety of different scenarios have been put forward. By combining resonant photoemission, X-ray magnetic circular dichroism and density functional theory, we determine the local electronic and magnetic configurations of V and Cr impurities in (Bi,Sb)\(_2\)Te\(_3\). State-of-the-art first-principles calculations find pronounced differences in their 3d densities of states, and show how these impurity states mediate characteristic short-range pd exchange interactions, whose strength sensitively varies with the position of the 3d states relative to the Fermi level. Measurements on films with varying host stoichiometry support this trend. Our results explain, in an unified picture, the origins of the observed magnetic properties, and establish the essential role of impurity-state-mediated exchange interactions in the magnetism of MTI.
KW  - shape-truncation functions
KW  - semiconductors
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230686
VL  - 5
ER  - 
TY  - JOUR
A1  - Motyka, M.
A1  - Dyksik, M.
A1  - Ryczko, K.
A1  - Weih, R.
A1  - Dallner, M.
A1  - Höfling, S.
A1  - Kamp, M.
A1  - Sęk, G.
A1  - Misiewicz, J.
T1  - Type-II quantum wells with tensile-strained GaAsSb layers for interband cascade lasers with tailored valence band mixing
JF  - Applied Physics Letters
N2  - Optical properties of modified type II W-shaped quantum wells have been investigated with the aim to be utilized in interband cascade lasers. The results show that introducing a tensely strained GaAsSb layer, instead of a commonly used compressively strained GaInSb, allows employing the active transition involving valence band states with a significant admixture of the light holes. Theoretical predictions of multiband k.p theory have been experimentally verified by using photoluminescence and polarization dependent photoreflectance measurements. These results open a pathway for practical realization of mid-infrared lasing devices with uncommon polarization properties including, for instance, polarization-independent midinfrared light emitters.
KW  - modulation spectroscopy
KW  - semiconductors
KW  - Type-II quantum well
KW  - interband cascade laser
KW  - GaAsSb
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-189795
VL  - 108
IS  - 10
ER  - 
TY  - JOUR
A1  - Margapoti, E.
A1  - Alves, F. M.
A1  - Mahapatra, S.
A1  - Lopez-Richard, V.
A1  - Worschech, L.
A1  - Brunner, K.
A1  - Qu, F.
A1  - Destefani, C.
A1  - Menendez-Proupin, E.
A1  - Bougerol, C.
A1  - Forchel, A.
A1  - Marques, G. E.
T1  - Paramagnetic shift in thermally annealed Cd\(_x\)Zn\(_{1-x}\)Se quantum dots
JF  - New Journal of Physics
N2  - The photoluminescence of annealed Cd\(_x\)Zn\(_{1-x}\)Se quantum dots (QDs) under the influence of an external magnetic field has been studied in this paper. Post-growth annealing was performed for different annealing times. Above a critical annealing time, the QD luminescence shows a pronounced red-shift of the Zeeman split magnetic subcomponents. This observation is in contrast to the blue-shift caused by the diamagnetic behavior that is usually observed in non-magnetic QDs. We attribute our finding to the paramagnetism caused by the mixing of heavy and light hole states. Hence, post-growth thermal annealing treatment might be employed to render undoped epitaxial QDs intrinsically magnetic in a controlled manner. Two theoretical models were developed: a few-particle model to account for excitonic complex effects and a multiband calculation that describes the valence band hybridization. Contrasting the two models allowed us to unambiguously elucidate the nature of such an effect.
KW  - semiconductors
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-133294
VL  - 14
IS  - 043038
ER  - 
TY  - JOUR
A1  - Maaß, Henriette
A1  - Bentmann, Hendrik
A1  - Seibel, Christoph
A1  - Tusche, Christian
A1  - Eremeev, Sergey V.
A1  - Peixoto, Thiago R.F.
A1  - Tereshchenko, Oleg E.
A1  - Kokh, Konstantin A.
A1  - Chulkov, Evgueni V.
A1  - Kirschner, Jürgen
A1  - Reinert, Friedrich
T1  - Spin-texture inversion in the giant Rashba semiconductor BiTeI
JF  - Nature Communications
N2  - Semiconductors with strong spin–orbit interaction as the underlying mechanism for the generation of spin-polarized electrons are showing potential for applications in spintronic devices. Unveiling the full spin texture in momentum space for such materials and its relation to the microscopic structure of the electronic wave functions is experimentally challenging and yet essential for exploiting spin–orbit effects for spin manipulation. Here we employ a state-of-the-art photoelectron momentum microscope with a multichannel spin filter to directly image the spin texture of the layered polar semiconductor BiTeI within the full two-dimensional momentum plane. Our experimental results, supported by relativistic ab initio calculations, demonstrate that the valence and conduction band electrons in BiTeI have spin textures of opposite chirality and of pronounced orbital dependence beyond the standard Rashba model, the latter giving rise to strong optical selection-rule effects on the photoelectron spin polarization. These observations open avenues for spin-texture manipulation by atomic-layer and charge carrier control in polar semiconductors.
KW  - applied physics
KW  - spintronics
KW  - semiconductors
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-173769
VL  - 7
ER  - 
TY  - JOUR
A1  - Astakhov, Georgy V.
A1  - Fuchs, F.
A1  - Soltamov, V. A.
A1  - Väth, S.
A1  - Baranov, P. G.
A1  - Mokhov, E. N.
A1  - Dyakonov, V.
T1  - Silicon carbide light-emitting diode as a prospective room temperature source for single photons
JF  - Scientific Reports
N2  - Generation of single photons has been demonstrated in several systems. However, none of them satisfies all the conditions, e.g. room temperature functionality, telecom wavelength operation, high efficiency, as required for practical applications. Here, we report the fabrication of light-emitting diodes (LEDs) based on intrinsic defects in silicon carbide (SiC). To fabricate our devices we used a standard semiconductor manufacturing technology in combination with high-energy electron irradiation. The room temperature electroluminescence (EL) of our LEDs reveals two strong emission bands in the visible and near infrared (NIR) spectral ranges, associated with two different intrinsic defects. As these defects can potentially be generated at a low or even single defect level, our approach can be used to realize electrically driven single photon source for quantum telecommunication and information processing.
KW  - semiconductors
KW  - inorganic LEDs
KW  - quantum optics
KW  - nanophotonics
KW  - plasmonics
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-96308
ER  -