A realistic quantum capacitance model for quantum Hall edge state based Fabry-P\'{e}rot interferometers

In this work, the classical and the quantum capacitances are calculated for a Fabry-P\'{e}rot interferometer operating in the integer quantized Hall regime. We first consider a rotationally symmetric electrostatic confinement potential and obtain the widths and the spatial distribution of the insulating (incompressible) circular strips using a charge density profile stemming from self-consistent calculations. Modelling the electrical circuit of capacitors composed of metallic gates and incompressible/compressible strips, we investigate the conditions to observe Aharonov-Bohm (quantum mechanical phase dependent) and Coulomb Blockade (capacitive coupling dependent) effects reflected in conductance oscillations. In a last step, we solve the Schr\"odinger and the Poisson equations self-consistently in a numerical manner taking into account realistic experimental geometries. We find that, describing the conductance oscillations either by Aharanov-Bohm or Coulomb Blockade strongly depends on sample properties also other than size, therefore, determining the origin of these oscillations requires further experimental and theoretical investigation

The effect of sample properties on the electron velocity in quantum Hall bars

We report on our theoretical investigation of the effects of the confining potential profile and sample size on the electron velocity distribution in (narrow) quantum-Hall systems. The electrostatic properties of the electron system are obtained by the Thomas-Fermi-Poisson nonlinear screening theory. The electron velocity distribution as a function of the lateral coordinate is obtained from the slope of the screened potential at the Fermi level and within the incompressible strips (ISs). We compare our findings with the recent experiments.Comment: 8 pages, 6 figure

Ponašanja tvrdoće i povećanja gustoće prahova bakra i bronce kompaktiranih procesima hladnog prešanja u matrici smjerom jedne osi

In this study hardness and densification behaviour of copper and bronze powders under wet bag cold isostatic and uniaxial die pressing processes are examined. In uniaxial pressing the specimens were compacted up to a pressure of 800 MPa. Cold isostatic pressing (CIP) resulted in better densification for both of the studied powder materials. Attained densities were 94 % for copper and 82 % for bronze powders. In uniaxial die pressing greater pressurisation was needed to attain the same densification that obtained with CIP. The microhardness of both of the studied materials were measured before and after pressing processes. Higher pressure resulted in dislocation and strain hardening and increased hardness of powders.U ovom radu se istraživala promjena tvrdoće i povećanje gustoće prahova bakra i bronce prešanih na hladno u matrici smjerom jedne osi, te izostatski pomoću fluidnog medija. Pri hladnom prešanju u matrici smjerom jedne osi uzorci su kompaktirani s tlakovima do 800 MPa. Hladno izostatsko prešanje (CIP) rezultira znatnijim povećanjem gustoće kod oba praškasta materijala. Dobivene gustoće bile su 94 % za bakarni i 82 % za brončani prah. Kod prešanja u matrici smjerom jedne osi bilo je potrebno upotrijebiti veće tlakove da bi se postigla ista gustoća kao ona dobivena CIP postupkom. Mikrotvrdoća oba proučavana materijala mjerena je prije i nakon procesa prešanja. Veći tlakovi uzrokuju očvrščavanje dislokacijama i naprezanjem, te povećavaju tvrdoću prahova

The Anomalous X-Ray Pulsar 4U 0142+61: A Neutron Star with a Gaseous Fallback Disk

The recent detection of the anomalous X-ray pulsar (AXP) 4U 0142+61 in the mid-infrared with the {\it Spitzer} observatory by Z.Wang and coworkers constitutes the first instance of a disk around an AXP. We show, by analyzing earlier optical and near-IR data together with the recent data, that the overall broadband data set can be reproduced by a single model of an irradiated and viscously heated disk.Comment: 22 pages, 3 figures, minor revisons, appeared in Ap

Realistic modelling of quantum point contacts subject to high magnetic fields and with current bias at out of linear response regime

The electron and current density distributions in the close proximity of quantum point contacts (QPCs) are investigated. A three dimensional Poisson equation is solved self-consistently to obtain the electron density and potential profile in the absence of an external magnetic field for gate and etching defined devices. We observe the surface charges and their apparent effect on the confinement potential, when considering the (deeply) etched QPCs. In the presence of an external magnetic field, we investigate the formation of the incompressible strips and their influence on the current distribution both in the linear response and out of linear response regime. A spatial asymmetry of the current carrying incompressible strips, induced by the large source drain voltages, is reported for such devices in the non-linear regime.Comment: 16 Pages, 9 Figures, submitted to PR