Many-body effects in a quasi-one-dimensional electron gas (original) (raw)
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We apply density functional theory, in the local density approximation, to a quasi-one-dimensional electron gas in order to quantify the effect of Coulomb and correlation effects in modulating, and therefore patterning, the charge density distribution. Our calculations are presented specifically for surface-gate-defined quasi-one-dimensional quantum wires in a GaAs-AlGaAs heterostructure but we expect our results to apply more generally for other low dimensional semiconductor systems. We show that at high densities with strong confinement, screening of electrons in the direction transverse to the wire is efficient and density modulations are not visible. In the low-density, weak-confinement regime, the exchange-correlation potential induces small density modulations as the electrons are depleted from the wire. At the weakest confinements and lowest densities, the electron density splits into two rows thereby forming a pair of quantum wires that lie beneath the surface gates. An additional double-well external potential forms at very low density which enhances this row splitting phenomenon. We produce phase diagrams that show a transition between the presence of a single quantum wire in a split-gate structure and two quantum wires. We suggest that this phenomenon can be used to pattern and modulate the electron density in low-dimensional structures with particular application to systems where a proximity effect from a surface gate would be valuable.
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Curr Sci India 100 484 487, 2011
In this short article, a summary is presented of recent progress in understanding the behaviour of electrons in semiconductor nanostructures. The method of shaping the electron gas is by electrostatic confinement with split gates. Whereas a rigid one-dimensional system shows the canonical conductance quantization, the relaxation of confinement, towards two-dimensionality results in strong electron-electron repulsion, splitting the line of electrons into two separate rows. This situation is the precursor to the formation of a Wigner lattice and is an example of how the topology of the electron gas is determined by electron correlation.
Electron correlation and confinement effects in quasi-one-dimensional quantum wires at high density
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Ankush Girdhar, Vinod Ashokan, ∗ N. D. Drummond, Klaus Morawetz, 4 and K. N. Pathak † Department of Physics, Dr. B. R. Ambedkar National Institute of Technology, Jalandhar, Punjab 144011, India Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom Münster University of Applied Sciences, Stegerwaldstrasse 39, 48565 Steinfurt, Germany International Institute of PhysicsUFRN, Campus Universitário Lagoa nova, 59078-970 Natal, Brazil Centre for Advanced Study in Physics, Panjab University, Chandigarh 160014, India (Dated: February 23, 2022)
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Physical Review B, 2007
We demonstrate the trapping of a conduction electron between two identical adatom impurities in a onedimensional semiconductor quantum-dot array system ͑quantum wire͒. Bound steady states arise even when the energy of the adatom impurity is located in the continuous one-dimensional energy miniband. The steady state is a realization of the bound state in continuum ͑BIC͒ phenomenon first proposed by von Neuman and Wigner ͓Phys. Z. 30, 465 ͑1929͔͒. We analytically solve the dispersion equation for this localized state, which enables us to reveal the mechanism of the BIC. The appearance of the BIC state is attributed to the quantum interference between the impurities. The Van Hove singularity causes another type of bound state to form above and below the band edges, which may coexist with the BIC.
Nano Letters, 2012
Quantum point contacts (QPCs) have shown promise as nanoscale spin-selective components for spintronic applications and are of fundamental interest in the study of electron manybody effects such as the 0.7 × 2e 2 /h anomaly. We report on the dependence of the 1D Landé g-factor g * and 0.7 anomaly on electron density and confinement in QPCs with two different top-gate architectures. We obtain g * values up to 2.8 for the lowest 1D subband, significantly exceeding previous in-plane g-factor values in AlGaAs/GaAs QPCs, and approaching that in InGaAs/InP QPCs. We show that g * is highly sensitive to confinement potential, particularly for the lowest 1D subband. This suggests careful management of the QPC's confinement potential may enable the high g * desirable for spintronic applications without resorting to narrow-gap materials such as InAs or InSb. The 0.7 anomaly and zero-bias peak are also highly sensitive to confining potential, explaining the conflicting density dependencies of the 0.7 anomaly in the literature.
Exchange instability of the two-dimensional electron gas in semiconductor quantum wells
Physical Review B, 2002
A two-dimensional ͑2D͒ electron gas formed in a modulation-doped GaAs/Al x Ga 1Ϫx As single quantum well undergoes a first-order transition when the first excited subband is occupied with electrons, as the Fermi level is tuned into resonance with the excited subband by applying a dc voltage. Direct evidence for this effect is obtained from low-temperature photoluminescence spectra that display the sudden renormalization of the intersubband energy E 01 upon the abrupt occupation of the first excited subband. Calculations within densityfunctional theory, which treat the 2D exchange potential exactly, show that this thermodynamical instability of the electron system is mainly driven by intersubband terms of the exchange Coulomb interaction, thus being a unique but fundamental property of an electron system with more than one occupied subband.