Fractional quantum Hall effect in second subband of a 2DES

In the present paper we report on the experimental electron sheet density vs. magnetic field diagram for the magnetoresistance R(xx) of a two-dimensional electron system (2DES) with two occupied subbands. For magnetic fields above 9T, we found fractional quantum Hall levels centered around the filing factor v = 3/2 in both the two occupied electric subbands. We focused specially on the fractional levels of the second subband, whose experimental values of the magnetic field B of their minima do not obey a periodicity law in 1/|B-B(c)|, where B(c) is the critical field at the filling factor v = 3/2, and we explain this fact entirely in the framework of the composite fermions theory. We use a simple theoretical model to give a possible explanation for the fact. Copyright (c) EPLA, 2011

Reentrant quantum Hall effect in bilayer system at high filling factors

We report on the measurements of the quantum Hall effect states in double quantum well structures at the filling factors v = 4N + 1 and 4N + 3, where N is the Landau index number, in the presence of the in-plane magnetic field. The quantum Hall states at these filling factors vanish and reappear several times. Repeated reentrance of the transport gap occurs due to the periodic vanishing of the tunneling amplitude in the presence of the in-plane field. When the gap vanishes, the transport becomes anisotropic. The anisotropy persist at half-odd filling factors, when bilayer quantum Hall states are recovered with increase of the tilt angle. (C) 2007 Elsevier B.V. All rights reserved.

QUANTUM HALL FERROMAGNET IN A DOUBLE WELL WITH VANISHING g-FACTOR.

We have studied the quantum Hall effect in Al(x)Ga(1-x)As-double well structure with vanishing g-factor. We determined the density-magnetic field n(s) - B diagrams for the longitudinal resistance R(xx). In spite of the fact that the n(s) - B diagram for conventional GaAs double wells shows a striking similarity with the theory, we observed the strong difference between these diagrams for double wells with vanishing g-factor. We argue that the electron-electron interaction is responsible for unusual behavior of the Landau levels in such a system.

Spin Hall Effect in Symmetric Wells with Two Subbands

We investigate the spin Hall conductivity sigma (xy) (z) of a clean 2D electron gas formed in a two-subband well. We determine sigma (xy) (z) as arising from the inter-subband induced spin-orbit (SO) coupling eta (Calsaverini et al., Phys. Rev. B 78:155313, 2008) via a linear-response approach due to Rashba. By self-consistently calculating eta for realistic wells, we find that sigma (xy) (z) presents a non-monotonic (and non-universal) behavior and a sign change as the Fermi energy varies between the subband edges. Although our sigma (xy) (z) is very small (i.e., a parts per thousand(a)`` e/4 pi aEuro(3)), it is non-zero as opposed to linear-in-k SO models.

PL spectroscopy of Fermi electrons in regime of the quantum Hall effect

The influence of the interlayer coupling on formation of the quantized Hall phase at the filling factor v = 2 was studied in the multilayer GaAs/AlGaAs heterostructures The disorder broaden Gaussian photoluminescence line due to the localized electrons was found in the quantized Hall phase of the isolated multi-quantum well structure On the other hand. the quantized Hall phase of the weakly-coupled multilayers emitted an asymmetrical line similar to that one observed in the metallic electron systems. We demonstrated that the observed asymmetry indicates a formation of the Fermi Surface in the quantized Hall phase of the multilayer electron system due to the interlayer peicolation. A sharp decrease of the single-particle scattering time associated with the extended states oil the Fermi surface was observed at the filling factor v = 2. (C) 2009 Elsevier B.V All rights reserved

Influence of interlayer tunneling on the quantized Hall phases in intentionally disordered multilayer structures

Stability of the quantized Hall phases is studied in weakly coupled multilayers as a function of the interlayer correlations controlled by the interlayer tunneling and by the random variation of the well thicknesses. A strong enough interlayer disorder destroys the symmetry responsible for the quantization of the Hall conductivity, resulting in the breakdown of the quantum Hall effect. A clear difference between the dimensionalities of the metallic and insulating quantum Hall phases is demonstrated. The sharpness of the quantized Hall steps obtained in the coupled multilayers with different degrees of randomization was found consistent with the calculated interlayer tunneling energies. The observed width of the transition between the quantized Hall states in random multilayers is explained in terms of the local fluctuations of the electron density.

Compressibility of electron liquid in the quantized Hall phase of GaAs/AlGaAs multi-layers

Magneto-capacitance was studied in narrow miniband GaAs/AlGaAs superlattices where quasi-two dimensional electrons revealed the integer quantum Hall effect. The interwell tunneling was shown to reduce the effect of the quantization of the density of states on the capacitance of the superlattices. In such case the minimum of the capacitance observed at the filling factor nu = 2 was attributed to the decrease of the electron compressibility due to the formation of the incompressible quantized Hall phase. In accord with the theory this phase was found strongly inhomogeneous. The incompressible fraction of the quantized Hall phase was demonstrated to rapidly disappear with the increasing temperature. (C) 2008 Elsevier B.V. All rights reserved.

Spectroscopic evidence of extended states in quantized Hall phase of weakly coupled GaAs/AlGaAs multi-layers

The influence of the interlayer coupling on formation of the quantized Hall conductor phase at the filling factor v = 2 was studied in the multi-layer GaAs/AlGaAs heterostructures. The disorder broadened Gaussian photoluminescence line due to the localized electrons was found in the quantized Hall phase of the isolated multi-quantum well structure. On the other hand, the quantized Hall phase of the weakly coupled multi-layers emitted an unexpected asymmetrical line similar to that one observed in the metallic electron systems. We demonstrated that the observed asymmetry is caused by a partial population of the extended electron states formed in the quantized Hall conductor phase due to the interlayer percolation. A sharp decrease of the single-particle scattering time associated with these extended states was observed at the filling factor v = 2. (c) 2007 Elsevier B.V. All rights reserved.

Fan fictions eller adaptioner? : Om Amy Heckerlings spelfilm Clueless (1996) och Debra White Smiths roman Amanda (2006) mot Jane Austens roman Emma (1815)

Det huvudsakliga syftet med min uppsats var att utifrån originalverket Emma (1815) avJane Austen kunna bedöma vad två verk som inspirerats av romanen bör klassificeras som.De två verken var romanen Amanda (2006) av författaren Debra White Smith ochspelfilmen Clueless (1995) av regissören Amy Heckerling. Till min hjälp har jag lästaktuell forskning inom de två termerna adaption och fanfiction och utifrån detta gjort enjämförande analys på verken. Resultatet blev oväntat vagt, det visade sig att begreppen lågnärmre varandra än vad jag trott från början. Båda verken kan till viss del ses som enadaption på originalverket, på samma sätt som de även kan ses som fanfiction. Slutsatsenär dock att de båda verken passar bäst in under termen profic, som är en underkategoriinom fanfiction där författaren/regissören tjänar pengar på sin modifikation och intepublicerat verket i exempelvis ett obetalt nätforum som hobbyaktivitet.

L’infidélité dans le couple : Charles et Emma Bovary dans Madame Bovary de Flaubert et Dinah et Loulou dans Traversée de la Mangrove de Maryse Condé

Ce travail sur l’infidélité dans le couple traite les différentes sources de l’ennui ainsi que leurs conséquences dans la vie du couple. Les différentes opinions de différents auteurs sur la cause de l’infidélité dans le couple sont vues en long et en large. L’éducation féminine du XIXème siècle éclaire sur le handicap qui a entrainé certaines filles dans le malheur car l’éducation de l’époque ne les avait pas bien préparées pour devenir de bonnes épouses. Ce mémoire montre l’image de la religion dans ces deux oeuvres : Madame Bovary et Traversée de la mangrove. La question est de voir comment ces auteurs peignent la religion dans ces oeuvres et pourquoi ils adoptent l’infidélité pour sauver la femme de son ennui. Enfin, la comparaison de ces ennuis est faite afin de voir que dans ces couples, malgré le fait qu’ils appartiennent à des époques différentes, l’ennui dans le couple est le même. Ces auteurs ont procédé aux mêmes stratégies pour sauver le couple de son ennui. La morale critique et religieuse a été utilisée pour aborder ce thème, lorsque nous avons fait une lecture biblique de ces deux oeuvres.

Emma Garcia, Assistant Professor of Spanish

Emma Garcia, Assistant Professor of Spanish reading The Guardians: A Novel by Ana Castillo (PS3553.A8135 G83 2007)