2,819 research outputs found
Confinement of two-dimensional excitons in a non-homogeneous magnetic field
The effective Hamiltonian describing the motion of an exciton in an external
non-homogeneous magnetic field is derived. The magnetic field plays the role of
an effective potential for the exciton motion, results into an increment of the
exciton mass and modifies the exciton kinetic energy operator. In contrast to
the homogeneous field case, the exciton in a non-homogeneous magnetic field can
also be trapped in the low field region and the field gradient increases the
exciton confinement. The trapping energy and wave function of the exciton in a
GaAs two-dimensional electron gas for specific circular magnetic field
configurations are calculated. The results show than excitons can be trapped by
non-homogeneous magnetic fields, and that the trapping energy is strongly
correlated with the shape and strength of the non-homogeneous magnetic field
profile.Comment: 9 pages, 12 figure
BEC-BCS crossover in a cold and magnetized two color NJL model
The BEC-BCS crossover for a NJL model with diquark interactions is studied in
the presence of an external magnetic field. Particular attention is paid to
different regularization schemes used in the literature. A thorough comparison
of results is performed for the case of a cold and magnetized two-color NJL
model. According to our results, the critical chemical potential for the BEC
transition exhibits a clear inverse magnetic catalysis effect for magnetic
fields in the range . As for the BEC-BCS
crossover, the corresponding critical chemical potential is very weakly
sensitive to magnetic fields up to , showing a much smaller
inverse magnetic catalysis as compared to the BEC transition, and displays a
strong magnetic catalysis from this point on.Comment: 15 pages, 8 figures; v2 PRD versio
Exciton trapping in magnetic wire structures
The lateral magnetic confinement of quasi two-dimensional excitons into wire
like structures is studied. Spin effects are take into account and two
different magnetic field profiles are considered, which experimentally can be
created by the deposition of a ferromagnetic stripe on a semiconductor quantum
well with magnetization parallel or perpendicular to the grown direction of the
well. We find that it is possible to confine excitons into one-dimensional (1D)
traps. We show that the dependence of the confinement energy on the exciton
wave vector, which is related to its free direction of motion along the wire
direction, is very small. Through the application of a background magnetic
field it is possible to move the position of the trapping region towards the
edge of the ferromagnetic stripe or even underneath the stripe. The exact
position of this 1D exciton channel depends on the strength of the background
magnetic field and on the magnetic polarisation direction of the ferromagnetic
film.Comment: 10 pages, 7 figures, to be published in J. Phys: Condens. Matte
The Palaeozoic basement of the Andean Frontal Cordillera at 34º S (Cordón del Carrizalito, Mendoza Province, Argentina): Geotectonic implications
The Cordón del Carrizalito is located in the southern sector of the Andean Frontal Cordillera. In this area, the Andean basement is composed of meta-sedimentary rocks (Las Lagunitas Formation) of Ordovician age. In addition, no- or very low grade metamorphism and less deformed rocks also occur in the study area. We call these rocks Selerpe series, whose characteristics are comparable to other series, late Carboniferous in age, described in nearby areas. The Las Lagunitas Formation is affected by west-verging folds, developed under low-grade metamorphic conditions. These structures can be attributed to the Chanic orogeny (Late Devonian – early Carboniferous). The Selerpe series and Las Lagunitas Formation are deformed by east-verging thrusts and folds developed in narrow bands and generated in the absence or under very low metamorphic conditions. These structures always deform the Chanic structures, and are attributed to the Gondwanan deformation (San Rafael orogeny, late Carboniferous – Permian in age). The Chanic structures of the study area can be placed in the western branch and in the hinterland of the Chanic orogen, which was developed as a result of the accretion of the Chilenia terrane at the west Gondwana margin during Late Devonian and early Carboniferous. The eastern branch of this orogen is located in the Andean Precordillera. The Permo-Triassic cover, deformed by the Andean orogenic cycle (Mesozoic – Cenozoic), rests unconformably on the Palaeozoic basement rocks.En el Cordón del Carrizalito, situado en el sector meridional de la Cordillera Frontal de los Andes, afloran metasedimentos ordovÃcicos pertenecientes a la Formación Las Lagunitas y otro conjunto de rocas menos deformadas, en ausencia de metamorfismo o con metamorfisÂmo de muy bajo grado, que hemos denominado serie de Selerpe. Esta última es litoestratigráficamente comparable a series del CarbonÃfero superior descritas en áreas próximas. La Formación Las Lagunitas está afectada por pliegues apretados, vergentes al oeste y desarrollados bajo condiciones de metamorfismo de bajo grado. Estas estructuras pueden ser atribuidas a la orogenia Chánica (Devónico Superior - CarÂbonÃfero inferior). La deformación Gondwánica, atribuida a la orogenia San Rafael, (CarbonÃfero superior – Pérmico), afecta tanto a la serie de Selerpe como a la Formación Las Lagunitas y se caracteriza por cabalgamientos y pliegues vergentes al este y generados en ausencia de metamorfismo o bajo condiciones metamórficas de muy grado bajo. Las estructuras chánicas de la zona estudiada se encuentran en las zonas internas de la rama occidental del orógeno del mismo nombre. Estas estructuras se desarrollaron como resultado de la acreción del terreno de Chilenia al margen occidental del antiguo continente de Gondwana durante el Devónico Superior – CarbonÃfero inferior. La rama oriental del orógeno Chánico se sitúa en la Precordillera andina. La cobertera permo-triásica, deformada durante el Mesozoico y Cenozoico por el ciclo orogénico Andino, se apoya discordantemente sobre las rocas del basamento paleozoico
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