Capacitance of a Double-Heterojunction GaAs/AlGaAs Structure Subjected to In-Plane Magnetic Fields: Results of Self-Consistent Calculations

The capacitance of a double-heterojunction structure with a wide GaAs undoped layer embedded between two selectively doped AlGaAs barriers is calculated self-consistently as a function of intensity of the in-plane magnetic field. With increasing field intensity the capacitance initially increases and after reaching a maximum decreases toward a high field limit which is less than its zero field value. This behaviour is attributed to 'breathing', or charge redistribution, of the 2D electron gas at individual heterojunctions due to a combination of the confining potential and the magnetic field.Comment: LaTeX, 9 pages, 7 figs. available on request from [email protected] in 1 PS file (compressed and uuencoded

Capacitance of Gated GaAs/AlGaAs Heterostructures Subject to In-plane Magnetic Fields

A detailed analysis of the capacitance of gated GaAs/AlGaAs heterostructures is presented. The nonlinear dependence of the capacitance on the gate voltage and in-plane magnetic field is discussed together with the capacitance quantum steps connected with a population of higher 2D gas subbands. The results of full self-consistent numerical calculations are compared to recent experimental data.Comment: 4 pages, Revtex. 4 PostScript figures in an uuencoded compressed file available upon request. Phys. Rev.B, in pres

Resistance spikes and domain wall loops in Ising quantum Hall ferromagnets

We explain the recent observation of resistance spikes and hysteretic transport properties in Ising quantum Hall ferromagnets in terms of the unique physics of their domain walls. Self-consistent RPA/Hartree-Fock theory is applied to microscopically determine properties of the ground state and domain-wall excitations. In these systems domain wall loops support one-dimensional electron systems with an effective mass comparable to the bare electron mass and may carry charge. Our theory is able to account quantitatively for the experimental Ising critical temperature and to explain characteristics of the resistive hysteresis loops.Comment: 4 pages, 3 figure

Numerical Investigation on Asymmetric Bilayer System at Integer Filling Factor

Deformation of the easy-axis ferromagnetic state in asymmetric bilayer systems are investigated numerically. Using the exact diagonalization the easy-axis to easy-plane ferromagnetic transition at total filling factor 3 or 4 is investigated. At still higher filling, novel stripe state in which stripes are aligned in the vertical direction occurs. The Hartree-Fock energies of relevant ordered states are calculated and compared.Comment: 4 pages, 6 figures, Proceedings of EP2DS-15, to appear in Physica

Circuit model for spin-bottleneck resistance in magnetic-tunnel-junction devices

Spin-bottlenecks are created in magnetic-tunnel-junction devices by spatial inhomogeneity in the relative resistances for up and down spins. We propose a simple electrical circuit model for these devices which incorporates spin-bottleneck effects and can be used to calculate their overall resistance and magnetoresistance. The model permits a simple understanding of the dependence of device magnetoresistance on spin diffusion lengths, tunneling magnetoresistance, and majority and minority spin resistivities in the ferromagnetic electrodes. The circuit model is in a good quantitative agreement with detailed transport calculations.Comment: 4 pages, 3 figures, submitted to Phys. Rev.