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Collective effects of spin ordering in a quasi-one-dimensional degenerate electron gas are discussed. The total energy of the quasi-one-dimensional system, as well as the exchange contribution per particle, has been calculated by the Hartree-Fock method. It has been shown that spontaneous polarization can be observed in the system when a universal parameter related to the density of the particles satisfies the inequality r s ≥ 0.476. A comparative analysis of one-, two-, and three-dimensional systems has been performed. A general expression has been obtained for the total energy per particle as a function of the degree of polarization and dimension of the system. According to this expression, the possibility of spontaneous polarization in the system is closely correlated with the dimension of the system. [ABSTRACT FROM AUTHOR]

The S-matrix formalism is used to perform analytical calculations of the spectrum of quasi-stationary states of charge carriers in a core-shell quantum dot. Analytical expressions are obtained for the second-order perturbative corrections to the position and half-width of a quasi-stationary energy level, and level shifts are calculated numerically for a core-shell quantum dot in the presence of an electrostatic field. The corrections to level half-width due to Stark effect are analyzed as functions of level energy and barrier thickness. It is shown that there exists a level position Ecr such that the correction δΓ to the level half-width changes sign. An analytical expression for the quadratic Stark shift in a dc-biased quantum well is found in semiclassical approximation. It is shown that the corresponding correction δΓ to half-width also changes sign as energy passes through Ecr. As an example, the Stark shift is calculated for a core-shell quantum dot in the electrostatic field of an adjacent protein molecule. [ABSTRACT FROM AUTHOR]

The problem of the peak values of the longitudinal conductivity under integer quantum Hall effect conditions is studied. The limiting cases of sharp and smooth chaotic potentials are considered. In the case of a sharp chaotic potential, the first longitudinal conductivity peak (δ) obtained by the extrapolation of numerical data to an infinite sample size L→∞ is (0.55±0.03) e 2/ h. In the case of a smooth chaotic potential, the peak values of the longitudinal conductivity are independent of the Landau level number and decrease as the chaotic-potential correlation length λ increases. The results obtained for sharp and smooth chaotic potentials agree with the reported experimental and numerically calculated data. [ABSTRACT FROM AUTHOR]

Microscopic calculation of the probability of Auger recombination of charge carriers localized in a semiconducting quantum dot (QD) is carried out. It is shown that two mechanism of Auger recombination (nonthreshold and quasi-threshold) operate in the QD. The nonthreshold Auger recombination mechanism is associated with scattering of a quasimomentum from a heterobarrier, while the quasi-threshold mechanism is connected with spatial confinement of the wave functions of charge carriers to the QD region; scattering of carriers occurs at the short-range Coulomb potential. Both mechanisms lead to a substantial enhancement of Auger recombination at the QD as compared to a homogeneous semiconductor. A detailed analysis of the dependence of Auger recombination coefficient on the temperature and QD parameters is carried out. It is shown that the nonthreshold Auger recombination process dominates at low temperatures, while the quasi-threshold mechanism prevails at high temperatures. The dependence of the Auger recombination coefficient on the QD radius experiences noticeable changes as compared to quantum wells and quantum filaments. [ABSTRACT FROM AUTHOR]

An analysis is made of mechanisms for Auger recombination of nonequilibrium carriers in cylindrical quantum wires. It is shown that two different Auger recombination mechanisms take place in these wires: a quasi-threshold and a nonthreshold mechanism. Both mechanisms are associated with the presence of heterobarriers but are of a different nature. The quasi-threshold mechanism is attributed to the spatial confinement of the carrier wave functions to the region of the quantum wire and in this case the quasi-momentum conservation law is violated and the Auger recombination process is intensified. As the radius of the wire increases, the quasithreshold Auger recombination process goes over to a threshold process. The nonthreshold mechanism is caused by the scattering of an electron (hole) at the heterojunction; the rate of this nonthreshold Auger recombination tends to zero in the limit of an infinite-radius wire. [ABSTRACT FROM AUTHOR]

The main mechanisms for the Auger recombination of nonequilibrium carriers in semiconductor quantum-well heterostructures are investigated. It is shown for the first time that there are three fundamentally different Auger recombination mechanisms in quantum wells: 1) a threshold-free mechanism, 2) a quasithreshold mechanism, and 3) a threshold mechanism. The rate of the threshold-free process has a weak temperature dependence. The rate of the quasithreshold Auger process exhibits an exponential temperature dependence. However, the threshold energy depends significantly on the quantum-well width and is close to zero for narrow quantum wells. It is shown that the threshold-free and quasithreshold processes are dominant in fairly narrow quantum wells, while the quasithreshold and threshold Auger processes are dominant in wide quantum wells. The limiting transition to a three-dimensional Auger process is accomplished for a quantum-well width tending to infinity. The value of the critical quantum-well width, at which the quasithreshold and threshold Auger processes combine to form a single three-dimensional Auger recombination process, is found. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]