Search results for "mesoscopic system"
showing 10 items of 587 documents
Inter- and intra-layer excitons in MoS$_2$/WS$_2$ and MoSe$_2$/WSe$_2$ heterobilayers
2018
Accurately described excitonic properties of transition metal dichalcogenide heterobilayers (HBLs) are crucial to comprehend the optical response and the charge carrier dynamics of them. Excitons in multilayer systems posses inter or intralayer character whose spectral positions depend on their binding energy and the band alignment of the constituent single-layers. In this study, we report the electronic structure and the absorption spectra of MoS$_2$/WS$_2$ and MoSe$_2$/WSe$_2$ HBLs from first-principles calculations. We explore the spectral positions, binding energies and the origins of inter and intralayer excitons and compare our results with experimental observations. The absorption sp…
Depolarization field in thin ferroelectric films with account of semiconductor electrodes
2004
Within the framework of the phenomenological Ginzburg-Landau theory influence of semiconductor electrodes on the properties of thin ferroelectric films is considered. The contribution of the semiconductor electrodes with different Debye screening length of carriers is included in functional of free energy. The influence of highly doped semiconductor electrodes on the depolarization field and the film properties was shown to be great.
Resonance fluorescence and laser spectroscopy of three-dimensionally confined excitons in monolayer WSe$_2$
2016
Resonant optical excitation of few-level quantum systems enables coherent quantum control, resonance fluorescence, and direct characterization of dephasing mechanisms. Experimental demonstrations have been achieved in a variety of atomic and solid-state systems. An alternative but intriguing quantum photonic platform is based on single layer transition metal chalcogenide semiconductors, which exhibit a direct band-gap with optically addressable exciton valley-pseudospins in a uniquely two-dimensional form. Here we perform resonance and near-resonance excitation of three-dimensionally confined excitons in monolayer WSe$_2$ to reveal near ideal single photon fluorescence with count rates up t…
On/off switching of bit readout in bias-enhanced tunnel magneto-Seebeck effect.
2014
Thermoelectric effects in magnetic tunnel junctions are currently an attractive research topic. Here, we demonstrate that the tunnel magneto-Seebeck effect (TMS) in CoFeB/MgO/CoFeB tunnel junctions can be switched on to a logic 1 state and off to 0 by simply changing the magnetic state of the CoFeB electrodes. We enable this new functionality of magnetic tunnel junctions by combining a thermal gradient and an electric field. This new technique unveils the bias-enhanced tunnel magneto-Seebeck effect, which can serve as the basis for logic devices or memories in a green information technology with a pure thermal write and read process. Furthermore, the thermally generated voltages that are re…
Interlayer exciton dynamics in van der Waals heterostructures
2018
Exciton binding energies of hundreds of meV and strong light absorption in the optical frequency range make transition metal dichalcogenides (TMDs) promising for novel optoelectronic nanodevices. In particular, atomically thin TMDs can be stacked to heterostructures enabling the design of new materials with tailored properties. The strong Coulomb interaction gives rise to interlayer excitons, where electrons and holes are spatially separated in different layers. In this work, we reveal the microscopic processes behind the formation, thermalization and decay of these fundamentally interesting and technologically relevant interlayer excitonic states. In particular, we present for the exemplar…
InAs/InP single quantum wire formation and emission at 1.5 microns
2006
Isolated InAs/InP self-assembled quantum wires have been grown using in situ accumulated stress measurements to adjust the optimal InAs thickness. Atomic force microscopy imaging shows highly asymmetric nanostructures with average length exceeding more than ten times their width. High resolution optical investigation of as-grown samples reveals strong photoluminescence from individual quantum wires at 1.5 microns. Additional sharp features are related to monolayer fluctuations of the two dimensional InAs layer present during the early stages of the quantum wire self-assembling process.
Writing and reading antiferromagnetic Mn
2017
Using antiferromagnets as active elements in spintronics requires the ability to manipulate and read-out the Néel vector orientation. Here we demonstrate for Mn2Au, a good conductor with a high ordering temperature suitable for applications, reproducible switching using current pulse generated bulk spin-orbit torques and read-out by magnetoresistance measurements. Reversible and consistent changes of the longitudinal resistance and planar Hall voltage of star-patterned epitaxial Mn2Au(001) thin films were generated by pulse current densities of ≃107 A/cm2. The symmetry of the torques agrees with theoretical predictions and a large read-out magnetoresistance effect of more than ≃6% is reprod…
Диссипативное туннелирование электронов в вертикально связанных двойных асимметричных квантовых точках InAs/GaAs(001)
2021
We report on the results of experimental studies of the photoelectric properties of a GaAs p-i-n photodiode with InAs/GaAs(001) double asymmetric quantum dots (DAQDs) grown by self-assembling in Metal Organic Vapor Phase Epitaxy (MOVPE) process. Three peaks were observed in the dependence of the photocurrent on the reverse bias measured at monochromatic photoexcitation of the DAQDs at the wavelength corresponding to the energy of interband optical transitions between the ground hole and electron states in the bigger QDs. These peaks were related to the tunneling of the photoexcited electrons between the QDs including the dissipative one (with emission and absorption of the optical phonons)…
Giant Negative Magnetoresistance Driven by Spin-Orbit Coupling at the LaAlO3/SrTiO3 Interface
2015
The LaAlO3/SrTiO3 interface hosts a two-dimensional electron system that is unusually sensitive to the application of an in-plane magnetic field. Low-temperature experiments have revealed a giant negative magnetoresistance (dropping by 70%), attributed to a magnetic-field induced transition between interacting phases of conduction electrons with Kondo-screened magnetic impurities. Here we report on experiments over a broad temperature range, showing the persistence of the magnetoresistance up to the 20 K range--indicative of a single-particle mechanism. Motivated by a striking correspondence between the temperature and carrier density dependence of our magnetoresistance measurements we prop…
Exciton recombination dynamics in InAs∕InP self-assembled quantum wires
2005
In this work we investigate the exciton recombination dynamics in InAs∕InP semiconductor self-assembled quantum wires, by means of continuous wave and time resolved photoluminescence. The continuous wave photoluminescence results seem to indicate that the temperature quenching of the emission band seems to be more probably due to unipolar thermal escape of electrons towards the InP barrier. On the other hand, the analysis of time resolved photoluminescence reveals that the temperature dependence of the radiative and nonradiative recombination times is mainly determined by the dynamics of excitons localized by disorder (high energy tail of the PL band) and strongly localized (low energy tail…