Showing papers by "Peter H. Beton published in 1990"
TL;DR: The magnetoresistance of a two-dimensional electron gas subjected to a periodic potential of variable amplitude is investigated, with results that explain the broadening of the Landau levels within a semiclassical model of electron transport.
Abstract: We have investigated the magnetoresistance of a two-dimensional electron gas subjected to a periodic potential of variable amplitude. The periodic potential, of period 300 nm, is generated with use of a gate deposited over a layer of patterned resist, and its amplitude is controlled by the gate voltage. At low gate voltages, two series of oscillations periodic in inverse magnetic field are observed. One series, at low magnetic field, is due to the periodic potential and the other is the usual Shubnikov--de Haas oscillations. The application of a small gate voltage generates an increase in the amplitude of the low-field oscillations, followed by a quenching of these oscillations as the gate voltage is increased further. In addition, a low-field positive magnetoresistance is generated, becoming larger with increasing gate voltage. These effects are explained within a semiclassical model of electron transport. Also the Shubnikov--de Haas oscillations quench as the amplitude of the potential increases. This is explained in terms of a broadening of the Landau levels.
82 citations
TL;DR: On observe une serie d'oscillations periodiques, dans des champs faibles inverses, dues a une derive resonnante des electrons dans le potentiel periodique.
Abstract: We have measured the magnetoresistance at various temperatures of a two-dimensional electron gas subjected to a one-dimensional periodic potential. A series of oscillations periodic in inverse magnetic field is observed at low fields due to a resonant drift of electrons in the periodic potential, while at higher fields the Shubnikov--de Haas (SdH) oscillations are observed. The low-field oscillations persist to a much higher temperature than the SdH oscillations. We argue that the low-field oscillations are quenched when the thermal smearing of the cyclotron orbit diameter is equal to the period of the potential. Using this simple model, we show that the temperature at which the low-field oscillations are quenched is larger than that for the SdH oscillations by a factor ${\mathit{k}}_{\mathit{F}}$a/2, where a is the period and ${\mathit{k}}_{\mathit{F}}$ the Fermi wave vector. In addition, an explicit expression for the temperature dependence of the low-field oscillations is calculated and compared with our experimental data. Excellent agreement is found between the predicted and observed temperature dependences.
33 citations
TL;DR: The thermopower of small ${\mathit{n}}^{+}$-GaAs wires is measured using a novel electron heating technique and the results show very large fluctuations which are in good agreement with existing theories.
Abstract: We have measured the thermopower of small ${\mathit{n}}^{+}$-GaAs wires using a novel electron heating technique. The results show very large fluctuations which are in good agreement with existing theories. We believe this to be the first observation of universal thermopower fluctuations.
28 citations
TL;DR: In this paper, the magnetoresistance and Hall resistance of an open-cross structure formed in a two-dimensional electron gas by electrostatic depletion was measured and interpreted using the classical model of Beenakker and van Houten (1989).
Abstract: The authors have measured the magnetoresistance and Hall resistance of an open-cross structure formed in a two-dimensional electron gas by electrostatic depletion. They observe effects similar to those seen by other authors in more closed geometries. They interpret results using the classical model of Beenakker and van Houten (1989). By measuring the ballistic transmission coefficient directly they are able to provide quantitative confirmation of the model.
9 citations
TL;DR: In this paper, the existence of Universal Thermopower and AC Rectification Fluctuations in a submicron n + GaAs wire was shown. But it was not shown that AC rectification is universal.
1 citations
TL;DR: In this article, a new technique for studying changes in the microscopic configuration of charged scatterers in doped semiconductors is presented, based on Universal Conductance Fluctuations (UCF).
Abstract: We present a new technique for studying changes in the microscopic configuration of charged scatterers in doped semiconductors. The technique is based on Universal Conductance Fluctuations (UCF). To illustrate the process we describe experiments on Si-doped GaAs wires fabricated using electron-beam lithography. By pulsing an infra-red LED we are able to depopulate meta-stable charge traps in the wire. We also investigate changes in the scattering configuration due to thermal cycling.
1 citations
TL;DR: In this paper, the authors present the first observations of rectification fluctuations in a mesoscopic conductor; a small n+-GaAs wire, which enables them to examine directly that part of the conductance fluctuation that is antisymmetric in the applied voltage.
Abstract: The authors present the first observations of rectification fluctuations in a mesoscopic conductor; a small n+-GaAs wire. The results obtained enable them to examine directly that part of the conductance fluctuation that is antisymmetric in the applied voltage. Analysis of the data in terms of the ratio of the antisymmetric and normal conductance fluctuations then gives excellent quantitative agreement with the theoretical predictions.
TL;DR: In this paper, the temperature dependence of low field series of oscillations observed in the magnetoresistance of a two dimensional electron gas subjected to a periodic potential was measured, and the experimental results were compared with an expression calculated using the Kubo formalism and find good agreement between theory and experiment.
Abstract: We have measured the temperature dependence of the low field series of oscillations which are observed in the magnetoresistance of a two dimensional electron gas subjected to a periodic potential. We compare our experimental results with an expression we have calculated using the Kubo formalism and find good agreement between theory and experiment. In addition we present experimental evidence of the quenching of the low field oscillations by a magnetic field applied in the plane of the two dimensional electron gas.
TL;DR: In this article, the authors measured the series resistance of two ballistic resistors or quantum point contacts in two configurations: collinear resistors and point contacts perpendicular to each other, and found that in zero field the resistances add classically but that the transmission coefficient increases if either the magnetic field or the width of the constriction in the resistors is increased.
Abstract: The authors have measured the series resistance of two ballistic resistors, or quantum point contacts, in two configurations. First when the resistors are collinear they measure the series resistance and the intermediate voltage between the resistors. Using a simple model they calculate the ballistic transport coefficient from the data. They find that the highest values are obtained when one channel is much wider than the other. Poorest transmission is always obtained when the two channels are identical. Secondly, they investigate two quantum point contacts perpendicular to each other. They find that in zero field the resistances add classically but that the transmission coefficient increases if either the magnetic field or the width of the constriction in the ballistic resistors is increased.