Evanescent incompressible strips as origin of the observed Hall resistance overshoot

In this work we provide a systematic explanation to the unusual non-monotonic behavior of the Hall resistance observed at two-dimensional electron systems. We use a semi-analytical model based on the interaction theory of the integer quantized Hall effect to investigate the existence of the anomalous, \emph{i.e} overshoot, Hall resistance $R_{H}$. The observation of the overshoot resistance at low magnetic field edge of the plateaus is elucidated by means of overlapping evanescent incompressible strips, formed due to strong magnetic fields and interactions. Utilizing a self-consistent numerical scheme we also show that, if the magnetic field is decreased the $R_{H}$ decreases to its expected value. The effects of the sample width, temperature, disorder strength and magnetic field on the overshoot peaks are investigated in detail. Based on our findings, we predict a controllable procedure to manipulate the maxima of the peaks, which can be tested experimentally. Our model does not depend on specific and intrinsic properties of the material, provided that a single particle gap exists.Comment: A theoretical follow-up paper of arXiv:1007.258

Exchange-correlation enhancement of the Lande-g* factor in integer quantized Hall plateaus

We study the emergent role of many-body effects on a two dimensional electron gas (2DEG) within the Thomas-Fermi-Poisson approximation, including both the exchange and correlation interactions in the presence of a strong perpendicular magnetic field. It is shown that, the indirect interactions widen the odd-integer incompressible strips spatially, whereas the even-integer filling factors almost remain unaffected.Comment: 8 pages,4 figure

Interaction mediated asymmetries of the quantized Hall effect

Experimental and theoretical investigations on the integer quantized Hall effect in gate defined narrow Hall bars are presented. At low electron mobility the classical (high temperature) Hall resistance line RH(B) cuts through the center of all Hall plateaus. In contrast, for our high mobility samples the intersection point, at even filling factors \nu = 2; 4 ..., is clearly shifted towards larger magnetic fields B. This asymmetry is in good agreement with predictions of the screening theory, i. e. taking Coulomb interaction into account. The observed effect is directly related to the formation of incompressible strips in the Hall bar. The spin-split plateau at \nu= 1 is found to be almost symmetric regardless of the mobility. We explain this within the so-called effective g-model.Comment: 4 pages, 3 figure

Energy calculations of quantum dot

We calculated the total energy of a semiconductor quantum dot formed in gate and etching defined devices. A 3D Poisson equation is solved self-consistently to obtain the electron density and potential profile. The total energies of electrons in the quantum dots with two different sizes are calculated with three different approximations by using the density and potential obtained from self-consistent procedure. In our calculation we used a recently developed energy functional called "orbital-free energy functional", Thomas-Fermi approximation and standard local-density approximation within density functional theory. The comparison of these methods reveals the efficacy of the used newly developed orbital-free energy functional which facilitates the calculation of Hartree integral for treatment of electron-electron interaction. (C) 2011 Elsevier B.V. All rights reserved

Structural and electronic properties of GaxTl 1 - xP ternary alloys

© 2015 Elsevier Ltd.The structural and electronic properties of GaxTl1-xP ternary alloys in zincblende phase were studied using pseudopotential plane wave method within the density functional theory. The dependence of the lattice parameter, bulk modulus, its pressure derivative, electronic structure, energy band gap and optical bowing on the composition x were analyzed for 0<x<1 with small increments, disregarding the so long computational time. The lattice parameters were optimized exhibiting linear concentration dependence in accordance with Vegards law. The bulk modulus as a function of gallium composition shows linear-like concentration dependence with a large upward bowing parameter equal to 10.79 GPa. We found that the band gap increases with increasing compositions of Ga, so that the compounds change from metal to semiconducting phase and could be useful for device applications in spintronics, especially at certain contributions. As a consequence the band gap bowing is found to be strongly composition dependent. The microscopic origins of the gap bowing were detailed and explained according to Zunger approach