SINGLE-PARTICLE SUBBAND SPECTROSCOPY IN A PARABOLIC QUANTUM-WELL VIA TRANSPORT EXPERIMENTS

Article

关键词: DIMENSIONAL ELECTRON-GAS;    PARALLEL MAGNETIC-FIELD;    SPACE-CHARGE LAYER;    INTERSUBBAND SCATTERING;    INVERSION-LAYERS;    HALL REGIME;    HETEROJUNCTIONS;    GAAS;    DEPOPULATION;    SYSTEM;   

DOI  :  10.1103/PhysRevB.47.1366

来源: SCIE

【 摘 要 】

The transport properties of a parabolic quantum well are investigated at low temperatures 0.5 K < T < 4 K. A front-gate voltage is used to tune the carrier density and hence the subband structure over a wide range. Various orientations of a magnetic field B with respect to the normal of the sample 0-degrees less-than-or-equal-to alpha less-than-or-equal-to 90-degrees are investigated. For alpha = 0-degrees, where B is oriented along the surface normal of the sample, quantum Hall states can be suppressed and recovered depending on the carrier density of the sample. This effect is explained quantitatively by a self-consistent calculation that considers the interplay of occupied Landau levels belonging to different subbands. A suppressed quantum Hall state can also be recovered via a tilted magnetic field. The resonant-subband-Landau-level coupling leads to a repulsion of the levels and, therefore, to the creation of an energy gap. For T < 0.5 K the spin splitting of the Landau levels appears in the magnetoresistance. In the regime of carrier densities where the quantum Hall plateau corresponding to filling factor nu = 4 is suppressed, a double minimum structure for nu = 3 is observed, reflecting the different exchange enhancement of the spin splitting of the two lowest subbands. For magnetic fields oriented in the plane of the sample, a band structure arises that leads to an anisotropic conductivity for current flow perpendicular and parallel to the magnetic-field orientation.

【 授权许可】

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