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We investigated the effect of perpendicular magnetic field on quantum wires when the spin-orbit interaction (SOI) of electrons is not neglected. Based on the calculated energy dispersion, the nonlinear ballistic conductance (G) and electron-diffusion thermoelectric power (Sd) are calculated as functions of the electron density, temperature and applied bias voltage. A low-temperature half-step feature in G that was observed experimentally by Quay et al. [Nat. Phys. 6, 336 (2010)], as well as a new peak in Sd are reproduced here in the low density region. These phenomena are related to the occurrence of Zeeman splitting and a SOI induced saddle point in the band structure where the channel chemical potential lies within an anticrossing gap between the saddle point of the lower subband and the bottom of the upper subband. Additionally, side peaks in G that are far away from the zero bias for the nonlinear transport, as well as a quadratic bias-voltage dependence of G near zero voltage, are predicted and discussed. [ABSTRACT FROM AUTHOR]

We calculated the effects of spin-orbit interaction on the energy bands, ballistic conductance (G), and the electron-diffusion thermoelectric power (Sd) of a nanowire by varying the temperature, electron density, and width of the wire. The potential barriers at the edges of the wire are assumed to be very high. A consequence of the boundary conditions used in this model is determined by the energy band structure, resulting in wider plateaus when the electron density is increased due to larger energy-level separation as the higher subbands are occupied by electrons. The nonlinear dependence of the transverse confinement on position with respect to the well center excludes the 'polelike feature' in G which is obtained when a harmonic potential is employed for confinement. At low temperature, Sd increases linearly with T but deviates from the linear behavior for large values of T. [ABSTRACT FROM AUTHOR]

We have investigated the conditions necessary to achieve stronger Cherenkov-like instability of plasma waves leading to emission in the terahertz regime for semiconductor quantum wells. The surface response function is calculated for a bilayer two-dimensional electron gas (2DEG) system in the presence of a periodic spatial modulation of the equilibrium electron density. The 2DEG layers are coupled to surface plasmons arising from excitations of free carriers in the bulk region between the layers. A current is passed through one of the layers and is characterized by a drift velocity vD for the driven electric charge. By means of a surface response function formalism, the plasmon dispersion equation is obtained as a function of frequency ω, in-plane wave vector q∥=(qx,qy), and reciprocal lattice vector nG, where n=0,±1,±2,... and G=2π/d, with d denoting the period of the density modulation. The dispersion equation, which yields the resonant frequencies, is solved numerically in the complex ω-plane for the real wave vector q∥. It is ascertained that the imaginary part of ω is enhanced with decreasing d and with increasing doping density of the free carriers in the bulk medium for a fixed period of the spatial modulation. [ABSTRACT FROM AUTHOR]