Showing papers on "Magnetocapacitance published in 1997"
TL;DR: In this paper, an ac capacitance measurement between the two-dimensional electron system (2DES) and the gate on GaAs/AlGaAs was performed, and it was found that the measured capacitance consists of the contribution from the edge states and that of the bulk state, which was treated as a distributed circuit of a resistive plate with the conductivity σxx.
Abstract: The quantum Hall effect for the GaAs/AlGaAs heterostrcture is investigated by an ac capacitance measurement between the two-dimensional electron system (2DES) and the gate on GaAs/AlGaAs. The capacitance minima at the quantum Hall plateaus are mainly determined not by the 2DES area under the gate but by the edge length of 2DES. There exists the high conductive region due to the edge states along the 2DES boundary, when the bulk conductivity σxx is small enough at low temperatures and high magnetic fields. From the temperature and frequency dependence of the capacitance minima, it is found that the measured capacitance consists of the contribution from the edge states and that of the bulk state, which is treated as a distributed circuit of a resistive plate with the conductivity σxx. The evaluated width of edge states from the capacitance is much larger than the magnetic length and the cyclotron radius expected from the one-electron picture. This wide width of edge states can be explained by the compressible-incompressible strip model, in which the screening effect is taken into account. Further the bulk conductivity of less than 10-12 S (S=1/Ω) is measured by the capacitance of the Corbino geometry sample, where the edge states are absent and the capacitance is determined by only σxx in this geometry. The localization of the bulk state is investigated by the obtained σxx.
5 citations
3 citations
TL;DR: In this article, the magnetic-field-induced carrier freeze-out in an n-type InSb sample has been investigated at 4.2 K in a magnetic field range from 0 to 7.0 T. The experimental results are compared with both theoretical and other experimental data.
Abstract: Magnetocapacitance spectroscopy is introduced to study the magnetic-field-induced carrier freeze-out in narrow-gap semiconductors (NGS). By using this experimental method the magnetic-field-induced carrier freeze-out in an n-type InSb sample has been investigated at 4.2 K in a magnetic field range from 0 to 7.0 T. With increasing magnetic field between 2.0 T and 7.0 T, the activation energy of shallow donors in the sample increased from about 1.0 meV to 2.7 meV. The experimental results are compared with both theoretical and other experimental data. Good agreement is obtained between our experimental results and others, while discrepancies still exist between the experiment and theory.
2 citations
TL;DR: In this paper, the flatband magnetocapacitance measurement was introduced to study magnetotransport properties in bulk semiconductors, which can avoid some problems inherent to the latter method, such as the influence of the surface conducting layer, the carrier mobility, and sample geometry correction factor.
Abstract: We introduce the flatband magnetocapacitance measurement to study magnetotransport properties in bulk semiconductors. This method is better, in some cases, than the Hall measurement because it can avoid some problems inherent to the latter method, such as the influence of the surface conducting layer, the carrier mobility, and the sample geometry correction factor. By using this experimental method some interesting phenomena concerning magnetotransport properties in an n-type InSb sample were observed, including Shubnikov–de Haas oscillations, resonant defect states, conduction process transitions, and the metal–insulator phase transition. The experimentally determined magnetotransport properties for the InSb sample are compared with those reported in literature.
1 citations
TL;DR: In this article, a theory for the magnetocapacitance of a partially screened two-dimensional (2D) electron gas is proposed, which is sensitive to different types of screening in a 2D electron gas with an integer filling factor.
Abstract: A theory for the magnetocapacitance of a partially screened two-dimensional (2D) electron gas is proposed. The model investigated is sensitive to different types of screening in a 2D electron gas with an integer filling factor: the so-called conventional approach and the self-consistent approximation introduced in the present paper. The calculations point to the importance of the self-consistent treatment of the magnetocapacitance of a 2D electron gas under the conditions of an integer filling factor. The final self-consistent results are qualitatively consistent with the available experimental data.
TL;DR: In this article, the authors investigated the ν = 1 3 and 2 3 fractional-quantum-Hall-effect (FQHE) states in gated GaAs/AlGaAs heterojunctions with tuned electron areal density.
Abstract: By the method of capacitance spectroscopy and of magnetotransport we have investigated the ν= 1 3 and 2 3 fractional-quantum-Hall-effect (FQHE) states in gated GaAs/AlGaAs heterojunctions with tuned electron areal density. Our experimental results confirm the theoretical prediction of the fractional quasiparticle charge e ∗ =e/3 in the ν= 1 3 FQHE state and of the existence of spin-aligned quasiholes and spin-reversed quasielectrons in the fully spin-polarized ν= 2 3 FQHE state.