Search results for "Quantum Hall effect"
showing 10 items of 622 documents
Inhomogeneous electron distribution in InN nanowires: Influence on the optical properties
2012
In this work, we study theoretically and experimentally the influence of the surface electron accumulation on the optical properties of InN nanowires. For this purpose, the photoluminescence and photoluminescence excitation spectra have been measured for a set of self-assembled InN NWs grown under different conditions. The photoluminescence excitation experimental lineshapes have been reproduced by a self-consistent calculation of the absorption in a cylindrical InN nanowires. With the self-consistent model we can explore how the optical absorption depends on nanowires radius and doping concentration. Our model solves the Schrodinger equation for a cylindrical nanowire of infinite length, a…
Impact of Annealing Temperature on Tunneling Magnetoresistance Multilayer Stacks
2020
The effect of annealing temperatures on the tunnel magnetoresistance (TMR) of MgO-based magnetic tunnel junctions (MTJs) has been investigated for annealing between 190 and 370°C. The TMR shows a maximum value of 215% at an annealing temperature of 330°C. A strong sensitivity of the TMR and the exchange bias of the pinned ferromagnetic layers on the annealing temperature are observed. Depending on sensor application requirements, the MTJ can be optimized either for stability and pinning strength or for a high TMR signal by choosing the appropriate annealing temperature. The switching mechanism of the ferromagnetic layers in the MTJ and the influence of the annealing on the layer properties,…
Influence of surface topography on depth profiles obtained by Rutherford backscattering spectrometry
2000
A method for determining correct depth profiles from samples with rough surfaces is presented. The method combines Rutherford backscattering spectrometry with atomic force microscopy. The topographical information obtained by atomic force microscopy is used to calculate the effect of the surface roughness on the backscattering spectrum. As an example, annealed Au/ZnSe heterostructures are studied. Gold grains were observed on the surfaces of the annealed samples. The annealing also caused diffusion of gold into the ZnSe. Backscattering spectra of the samples were measured with a 2 MeV 4He+ ion beam. A scanning nuclear microprobe was used to verify the results by measuring backscattering fro…
Magnetic properties of exciton trapped by an off-center ionized donor in single quantum dot
2021
Abstract It is known that the lines of exciton (X) and exciton trapped by an ionized donor ( D + , X ) are often very close which makes very difficult their experimental identification. In order to facilitate their distinction in spherical quantum dots, we investigate the effect of an applied magnetic field studying the binding energy of the complex ( D + , X ) as function of dot size and the ionized donor position. Our calculation is using a variational approach taking into account the interactions between all charge carriers. Our results show that the complex is more sensitive to the magnetic field than the exciton and that the energy of the exciton is not sufficiently affected when the i…
Giant, unconventional anomalous Hall effect in the metallic frustrated magnet candidate, KV 3 Sb 5
2020
The anomalous Hall effect soars when Dirac quasiparticles meet frustrated magnetism.
Trochoidal motion and pair generation in skyrmion and antiskyrmion dynamics under spin-orbit torques
2018
Magnetic skyrmions are swirling magnetic spin structures that could be used to build next-generation memory and logic devices. They can be characterized by a topological charge that describes how the spin winds around the core. The dynamics of skyrmions and antiskyrmions, which have opposite topological charges, are typically described by assuming a rigid core. However, this reduces the set of variables that describe skyrmion motion. Here we theoretically explore the dynamics of skyrmions and antiskyrmions in ultrathin ferromagnetic films and show that current-induced spin–orbit torques can lead to trochoidal motion and skyrmion–antiskyrmion pair generation, which occurs only for either the…
Prediction of ferroelectricity-driven Berry curvature enabling charge- and spin-controllable photocurrent in tin telluride monolayers
2019
In symmetry-broken crystalline solids, pole structures of Berry curvature (BC) can emerge, and they have been utilized as a versatile tool for controlling transport properties. For example, the monopole component of the BC is induced by the time-reversal symmetry breaking, and the BC dipole arises from a lack of inversion symmetry, leading to the anomalous Hall and nonlinear Hall effects, respectively. Based on first-principles calculations, we show that the ferroelectricity in a tin telluride monolayer produces a unique BC distribution, which offers charge- and spin-controllable photocurrents. Even with the sizable band gap, the ferroelectrically driven BC dipole is comparable to those of …
Out-of-plane orientation of luminescent excitons in two-dimensional indium selenide.
2019
Van der Waals materials offer a wide range of atomic layers with unique properties that can be easily combined to engineer novel electronic and photonic devices. A missing ingredient of the van der Waals platform is a two-dimensional crystal with naturally occurring out-of-plane luminescent dipole orientation. Here we measure the far-field photoluminescence intensity distribution of bulk InSe and two-dimensional InSe, WSe2 and MoSe2. We demonstrate, with the support of ab-initio calculations, that layered InSe flakes sustain luminescent excitons with an intrinsic out-of-plane orientation, in contrast with the in-plane orientation of dipoles we find in two-dimensional WSe2 and MoSe2 at room-…
Mapping an electron wave function by a local electron scattering probe
2015
A technique is developed which allows for the detailed mapping of the electronic wave function in two-dimensional electron gases with low-temperature mobilities up to $15\times {10}^{6}\;{\mathrm{cm}}^{2}\;{{\rm{V}}}^{-1}\;{{\rm{s}}}^{-1}$. Thin ('delta') layers of aluminium are placed into the regions where the electrons reside. This causes electron scattering which depends very locally on the amplitude of the electron wave function at the position of the Al δ-layer. By changing the distance of this layer from the interface we map the shape of the wave function perpendicular to the interface. Despite having a profound effect on the electron mobiliy, the δ-layers do not cause a widening of …
Effects of rapid thermal annealing on the optical properties of low-loss 1.3μm GaInNAs∕GaAs saturable Bragg reflectors
2004
We report studies of the effect of rapid thermal annealing (RTA) on the optical properties of a low-loss 1.3 mum saturable Bragg reflector (SBR), consisting of a GaInNAs/GaAs single quantum well embedded in an AlAs/GaAs Bragg reflector grown monolithically on a GaAs substrate. RTA gives rise to a blueshift of the photoluminescence (PL) peak (and therefore of the excitonic absorption peak) and an enhancement of PL intensity, while the reflectivity properties including peak reflectivity and bandwidth are not degraded. Temperature dependent photoluminescence measurements show that the RTA-induced blueshift of photoluminescence consists of two components: one originating from the increase of op…