102 research outputs found
Bound spin-excitons in two-dimensional electron gas
A theory of the spin exciton capture by a magnetic impurity in a 2D electron
gas is developed. We consider the resonance model for electron scattering by a
transition metal impurity and calculate the binding potential for spin
excitons. This potential is spin selective and is capable of binding a spin
exciton with zero angular momentum. In order to trap an exciton with a nonzero
angular momentum m, the potential must exceed a certain threshold value,
depending on m.Comment: 11 pages, 3 figure
Collective excitations in a magnetically doped quantized Hall ferromagnet
A theory of collective states in a magnetically quantized two-dimensional
electron gas (2DEG) with half-filled Landau level (quantized Hall ferromagnet)
in the presence of magnetic 3d impurities is developed. The spectrum of bound
and delocalized spin-excitons as well as the renormalization of Zeeman
splitting of the impurity 3d levels due to the indirect exchange interaction
with the 2DEG are studied for the specific case of n-type GaAs doped with Mn
where the Lande` g-factors of impurity and 2DEG have opposite signs. If the
sign of the 2DEG g-factor is changed due to external influences, then impurity
related transitions to new ground state phases, presenting various spin-flip
and skyrmion-like textures, are possible. Conditions for existence of these
phases are discussed. PACS: 73.43.Lp, 73.21.Fg, 72.15.RnComment: 32 pages including 7 figures. To be published in Phys. Rev.
Classical and quantum radiation of perturbed discrete breathers
We show that the linearized phase space flow around a discrete breather
solution is not capable of generating persistent energy flow away from the
breather even in the case of instabilities of extended states. This holds both
for the classical and quantized description of the flow. The main reason for
that is the parametric driving the breather provides to the flow. Corresponding
scaling arguments are derived for both classical and quantum cases. Numerical
simulations of the classical flow support our findings.Comment: 8 pages, 3 figure
Spin-engineered quantum dots
Spatially nonhomogeneously spin polarized nuclei are proposed as a new
mechanism to monitor electron states in a nanostructure, or as a means to
createn and, if necessary, reshape such nanostructures in the course of the
experiment. We found that a polarization of nulear spins may lift the spin
polarization of the electron states in a nanostructure and, if sufficiently
strong, leads to a polarization of the electron spins. Polarized nuclear spins
may form an energy landscape capable of binding electrons with energy up to
several meV and the localization radius 100\AA.Comment: 9 pages, 1 figure, submitted to Physica E, Augist 31, 200
Dynamics of Macroscopic Tunneling in Elongated BEC
We investigate macroscopic tunneling from an elongated quasi 1-d trap,
forming a 'cigar shaped' BEC. Using recently developed formalism we get the
leading analytical approximation for the right hand side of the potential wall,
i.e. outside the trap, and a formalism based on Wigner functions, for the left
side of the potential wall, i.e. inside the BEC. We then present accomplished
results of numerical calculations, which show a 'blip' in the particle density
traveling with an asymptotic shock velocity, as resulted from previous works on
a dot-like trap, but with significant differences from the latter. Inside the
BEC a pattern of a traveling dispersive shock wave is revealed. In the
attractive case, we find trains of bright solitons frozen near the boundary.Comment: 6 pages, 15 figure
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