194 research outputs found
Hysteresis effect due to the exchange Coulomb interaction in short-period superlattices in tilted magnetic fields
We calculate the ground-state of a two-dimensional electron gas in a
short-period lateral potential in magnetic field, with the Coulomb
electron-electron interaction included in the Hartree-Fock approximation. For a
sufficiently short period the dominant Coulomb effects are determined by the
exchange interaction. We find numerical solutions of the self-consistent
equations that have hysteresis properties when the magnetic field is tilted and
increased, such that the perpendicular component is always constant. This
behavior is a result of the interplay of the exchange interaction with the
energy dispersion and the spin splitting. We suggest that hysteresis effects of
this type could be observable in magneto-transport and magnetization
experiments on quantum-wire and quantum-dot superlattices.Comment: 3 pages, 3 figures, Revtex, to appear in Phys. Rev.
Combinatorial Heegaard Floer homology and nice Heegaard diagrams
We consider a stabilized version of hat Heegaard Floer homology of a
3-manifold Y (i.e. the U=0 variant of Heegaard Floer homology for closed
3-manifolds). We give a combinatorial algorithm for constructing this
invariant, starting from a Heegaard decomposition for Y, and give a
combinatorial proof of its invariance properties
Magnetization in short-period mesoscopic electron systems
We calculate the magnetization of the two-dimensional electron gas in a
short-period lateral superlattice, with the Coulomb interaction included in
Hartree and Hartree-Fock approximations. We compare the results for a finite,
mesoscopic system modulated by a periodic potential, with the results for the
infinite periodic system. In addition to the expected strong exchange effects,
the size of the system, the type and the strength of the lateral modulation
leave their fingerprints on the magnetization.Comment: RevTeX4, 10 pages with 14 included postscript figures To be published
in PRB. Replaced to repair figure
Finite size effects in the magnetization of periodic mesoscopic systems
We calculate the orbital magnetization of a confined 2DEG as a function of
the number of electrons in the system. Size effects are investigated by
systematically increasing the area of the confining region. The results for the
finite system are compared to an infinite one, where the magnetization is
calculated in the thermodynamic limit. In all calculations the
electron-electron interaction is included in the Hartree approximation.Comment: LaTeX with 4 PostScript figures included, to appear in EP2DS 13
proceeding
Thermoelectric current in topological insulator nanowires with impurities
In this paper we consider charge current generated by maintaining a
temperature difference over a nanowire at zero voltage bias. For topological
insulator nanowires in a perpendicular magnetic field the current can change
sign as the temperature of one end is increased. Here we study how this
thermoelectric current sign reversal depends on magnetic field and how
impurities affect the size of the thermoelectric current. We consider both
scalar and magnetic impurities and show that their influence on the current are
quite similar, although the magnetic impurities seem to be more effective in
reducing the effect. For moderate impurity concentration the sign reversal
persists.Comment: 8 pages, 3 figure
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