A5026500518- Semiconductor Quantum Structures and Devices
- Semiconductor Lasers and Optical Devices
- Quantum optics and atomic interactions
- Photonic and Optical Devices
- Organic Electronics and Photovoltaics
- Organic Light-Emitting Diodes Research
- Mechanical and Optical Resonators
- 2D Materials and Applications
- Atomic and Subatomic Physics Research
- Quantum Dots Synthesis And Properties
- Nanowire Synthesis and Applications
- Perovskite Materials and Applications
- Luminescence and Fluorescent Materials
- Acoustic Wave Phenomena Research
- Laser-Matter Interactions and Applications
- Quantum Information and Cryptography
- Metamaterials and Metasurfaces Applications
- Conducting polymers and applications
- Chalcogenide Semiconductor Thin Films
- Laser Design and Applications
- Quantum and electron transport phenomena
- Thermal properties of materials
- Molecular Junctions and Nanostructures
- Electronic and Structural Properties of Oxides
- Machine Learning in Materials Science
Freie Universität Berlin
2022-2024
Leibniz Institute for Solid State and Materials Research
2013-2019
University of Bayreuth
2008-2011
University of Potsdam
2008
Czech Academy of Sciences, Institute of Physics
2008
University of Bonn
1976
Mechanical strain is a powerful tuning knob for excitons, Coulomb-bound electron-hole complexes dominating optical properties of two-dimensional semiconductors. While the response bright free excitons broadly understood, behaviour dark (long-lived excitations that generally do not couple to light due spin and momentum conservation) or localized related defects remains mostly unexplored. Here, we study these fragile many-body states on pristine suspended WSe
Intervalley excitons with electron and hole wavefunctions residing in different valleys determine the long-range transport dynamics observed many semiconductors. However, these vanishing oscillator strength do not directly couple to light and, hence, remain largely unstudied. Here, we develop a simple nanomechanical technique control energy hierarchy of via their contrasting response mechanical strain. We use our discover previously inaccessible intervalley associated K, Γ, or Q prototypical...
Abstract A series of novel styrene derived monomers with triphenylamine‐based units, and their polymers have been synthesized compared the well‐known structure polymer N , ′‐bis(3‐methylphenyl)‐ ′‐diphenylbenzidine respect to hole‐transporting behavior in phosphorescent light‐emitting diodes (PLEDs). vinyltriphenylamine was selected as a basic unit, functionalized at para positions following side groups: diphenylamine, 3‐methylphenyl‐aniline, 1‐ 2‐naphthylamine, carbazole, phenothiazine. The...
Encoding and manipulating digital information in quantum degrees of freedom is one the major challenges today's science technology. The valley indices excitons transition metal dichalcogenides (TMDs) are well-suited to address this challenge. Here, we demonstrate a new class strain-tunable, valley-polarized hybrid monolayer TMDs, comprising pair energy-resonant intra- intervalley excitons. These states combine advantages bright intravalley excitons, where index directly couples light...
We demonstrate for the first time on-demand and wavelength-tunable single-photon emission from light-hole (LH) excitons in strain engineered GaAs quantum dots (QDs). The LH photon tensile-strained QDs is systematically investigated with polarization-resolved, power-dependent photoluminescence spectroscopy, photon-correlation measurements. By integrating QD-containing nanomembranes onto a piezo-actuator driving single picosecond laser pulses, we achieve triggered emission. Fourier transform...
We demonstrate an all-electrically operated wavelength-tunable on demand single-photon source for the first time. The device consists of a light-emitting diode in form semiconductor nanomembrane containing self-assembled quantum dots integrated onto piezoelectric crystal. Triggered single photons are generated via injection ultrashort electrical pulses into diode, while their energy can be precisely tuned over broad range by varying voltage applied to High speed operation this...
Long-distance fiber-based quantum communication relies on efficient non-classical light sources operating at telecommunication wavelengths. Semiconductor dots are promising candidates for on-demand generation of single photons and entangled photon pairs such applications. However, their brightness is strongly limited due to total internal reflection the semiconductor/vacuum interface. Here we overcome this limitation using a dielectric antenna structure. The source consists gallium phosphide...
We develop an effective model to describe the statistical properties of exciton fine structure splitting (FSS) and polarization angle in quantum dot ensembles (QDEs) using only a few symmetry-related parameters. The connection between random matrix theory is established. Such verified both theoretically experimentally several rather different types QDEs, each which contains hundreds thousands QDs. naturally addresses three fundamental issues regarding FSS angels are frequently encountered...
Abstract Although carbazole‐containing copolymers are frequently used as hole‐transporting host materials for polymer organic light‐emitting diodes (OLEDs), they often suffer from the formation of undesired exciplexes when OLED is operated. The reason why sometimes form electrical excitation, yet not optical excitation well understood. Here, we use luminescence measurements and quantum chemical calculations to investigate mechanism such exciplex (electroplex formation) in a...
Independent tuning of emission energy and decay time neutral excitons confined in single self-assembled In(Ga)As/GaAs quantum dots is achieved by simultaneously employing vertical electric fields lateral biaxial strain fields. By locking the via a closed-loop feedback on piezoelectric actuator used to control dot, we continuously decrease an exciton from 1.4 0.7 ns. Both perturbations are fully electrically controlled their combination offers promising route engineer indistinguishability...
We report on optical investigations of MOVPE-grown InGaAs/GaAs quantum dots emitting at the telecom O-band that were integrated onto uniaxial piezoelectric actuators. This promising technique, which does not degrade emission brightness emitters, enables us to tune dot wavelengths and their fine-structure splitting. By spectrally analyzing emitted light with respect its polarization, we are able demonstrate cancelation fine structure splitting within experimental resolution limit. work...
Abstract Cascading energy transfer is a usually undesired effect in organic‐host guest systems that are designed for light‐emitting purposes. Here we demonstrate chemical approach to suppressing from the blue red emitter multicomponent polymer blends. We have combined red, green and emitting Ir‐complex each with charge transporting molecules side‐chain copolymer. The covalent attachment of phosphorescent found prevent cascading through steric shielding. This approximately doubles efficiency...
Excitons in Transition Metal Dichalcogenides (TMDs) acquire a spin-like quantum number, pseudospin, originating from the crystal's discrete rotational symmetry. Here, we break this symmetry using tunable uniaxial strain, effectively generating pseudomagnetic field exceeding 40 Tesla. Under large field, demonstrate pseudospin analogs of spintronic phenomena such as Zeeman effect and Larmor precession. Moreover, determine previously inaccessible fundamental properties TMDs, including strength...
We report on optical investigations of MOVPE-grown InGaAs/GaAs quantum dots emitting at the telecom O-band that were integrated onto uniaxial piezoelectric actuators. This promising technique, which does not degrade quality or performances emitters, enables us to tune dot emission wavelengths and their fine-structure splitting. By spectrally analyzing emitted light with respect its polarization, we are able demonstrate cancelation fine structure splitting within experimental resolution...
Momentum-indirect excitons composed of electrons and holes in different valleys define optoelectronic properties many semiconductors, but are challenging to detect due their weak coupling light. The identification an excitons' valley character is further limited by complexities associated with momentum-selective probes. Here, we study the photoluminescence indirect controllably strained prototypical 2D semiconductors (WSe$_2$, WS$_2$) at cryogenic temperatures. We find that these i) exhibit...
Phononic crystals (PnCs) are artificially patterned media exhibiting bands of allowed and forbidden zones for phonons. Many emerging applications PnCs from solid-state simulators to quantum memories could benefit the on-demand tunability phononic band structure. Here, we demonstrate fabrication suspended graphene in which structure is controlled by mechanical tension applied electrostatically. We show signatures a mechanically tunable gap. The experimental data supported simulation suggest...
Abstract Phononic crystals (PnCs) are artificially patterned media exhibiting bands of allowed and forbidden zones for phonons—in analogy to the electronic band structure crystalline solids arising from periodic arrangement atoms. Many emerging applications PnCs solid-state simulators quantum memories could benefit on-demand tunability phononic structure. Here, we demonstrate fabrication suspended graphene in which is controlled by mechanical tension applied electrostatically. We show...