arXiv subjects

K. von Klitzing

Publications and source records attributed to K. von Klitzing.

30 records · Page 2Linked to original sources

arXiv2005

Circular polarization dependent study of the microwave photoconductivity in a two-dimensional electron system

The polarization dependence of the low field microwave photoconductivity and absorption of a two-dimensional electron system has been investigated in a quasi-optical setup in which linear and any circular polarization can be produced in-situ. The microwave induced resistance oscillations and the zero resistance regions are notedly immune to the sense of circular polarization. This observation is discrepant with a number of proposed theories. Deviations only occur near the cyclotron resonance absorption where an unprecedented large resistance response is observed.

cond-mat.mes-hall↗

arXiv2004

Radiation induced zero-resistance states in GaAs/AlGaAs heterostructures: Voltage-current characteristics and intensity dependence at the resistance minima

High mobility two-dimensional electron systems exhibit vanishing resistance over broad magnetic field intervals upon excitation with microwaves, with a characteristic reduction of the resistance with increasing radiation intensity at the resistance minima. Here, we report experimental results examining the voltage - current characteristics, and the resistance at the minima vs. the microwave power. The findings indicate that a non-linear V-I curve in the absence of microwave excitation becomes linearized under irradiation, unlike expectations, and they suggest a similarity between the roles of the radiation intensity and the inverse temperature.

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arXiv2004

Microwave photoresponse in the 2D electron system caused by intra-Landau level transitions

The influence of microwave radiation on the DC-magnetoresistance of 2D-electrons is studied in the regime beyond the recently discovered zero resistance states when the cyclotron frequency exceeds the radiation frequency. Radiation below 30 GHz causes a strong suppression of the resistance over a wide magnetic field range, whereas higher frequencies produce a non-monotonic behavior in the damping of the Shubnikov-de Haas oscillations. These observations are explained by the creation of a non-equilibrium electron distribution function by microwave induced intra-Landau level transitions.

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arXiv2004

Activated Transport in the individual Layers that form the $ν_T$=1 Exciton Condensate

We observe the total filling factor $ν_{T}$=1 quantum Hall state in a bilayer two-dimensional electron system with virtually no tunnelling. We find thermally activated transport in the balanced system with a monotonic increase of the activation energy with decreasing $d/\ell_B$ below 1.65. In the imbalanced system we find activated transport in each of the layers separately, yet the activation energies show a striking asymmetry around the balance point. This implies that the gap to charge-excitations in the {\em individual} layers is substantially different for positive and negative imbalance.

cond-mat.mes-hall↗

arXiv2004

Radiation induced oscillatory Hall effect in high mobility GaAs/AlGaAs devices

We examine the radiation induced modification of the Hall effect in high mobility GaAs/AlGaAs devices that exhibit vanishing resistance under microwave excitation. The modification in the Hall effect upon irradiation is characterized by (a) a small reduction in the slope of the Hall resistance curve with respect to the dark value, (b) a periodic reduction in the magnitude of the Hall resistance, $R_{xy}$, that correlates with an increase in the diagonal resistance, $R_{xx}$, and (c) a Hall resistance correction that disappears as the diagonal resistance vanishes.

cond-mat.mes-hall↗

arXiv2004

Radiation-induced oscillatory magnetoresistance as a sensitive probe of the zero-field spin splitting in high mobility GaAs/AlGaAs devices

We suggest an approach for characterizing the zero-field spin splitting of high mobility two-dimensional electron systems, when beats are not readily observable in the Shubnikov-de Haas effect. The zero-field spin splitting and the effective magnetic field seen in the reference frame of the electron is evaluated from a quantitative study of beats observed in radiation-induced magnetoresistance oscillations.

cond-mat.mes-hall↗

arXiv2004

Demonstration of a 1/4 cycle phase shift in the radiation-induced oscillatory-magnetoresistance in GaAs/AlGaAs devices

We examine the phase and the period of the radiation-induced oscillatory-magnetoresistance in GaAs/AlGaAs devices utilizing in-situ magnetic field calibration by Electron Spin Resonance of DiPhenyl-Picryl-Hydrazal. The results confirm a $f$-independent 1/4 cycle phase shift with respect to the $hf = j\hbarω_{c}$ condition for $j \geq 1$, and they also suggest a small ($\approx$ 2%) reduction in the effective mass ratio, $m^{*}/m$, with respect to the standard value for GaAs/AlGaAs devices.

cond-mat.mes-hall↗

arXiv2003

New type of $B$-periodic magneto-oscillations in a two-dimensional electron system induced by microwave irradiation

We observe a new type of magneto-oscillations in the photovoltage and the longitudinal resistance of a two-dimensional electron system. The oscillations are induced by microwave irradiation and are periodic in magnetic field. The period is determined by the microwave frequency, the electron density, and the distance between potential probes. The phenomenon is accounted for by coherent excitation of edge magnetoplasmons in the regions near the contacts and offers perspectives for the development of new tunable microwave and terahertz detection schemes and spectroscopic techniques.

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arXiv2003

Coulomb Drag as a Probe of the Nature of Compressible States in a Magnetic Field

Magneto-drag reveals the nature of compressible states and the underlying interplay of disorder and interactions. At ν=3/2 a clear T^{4/3} dependence is observed, which signifies the metallic nature of the N=0 Landau level. In contrast, drag in higher Landau levels reveals an additional contribution, which anomalously grows with decreasing T before turning to zero following a thermal activation law. The anomalous drag is discussed in terms of electron-hole asymmetry arising from disorder and localization, and the crossover to normal drag at high fields as due to screening of disorder.

cond-mat.mes-hall↗

arXiv2003

Quantum Hall Effect in a Two-Dimensional Electron System Bent by 90 Degrees

Using a new MBE growth technique, we fabricate a two-dimensional electron system which is bent around an atomically sharp 90 degree corner. In the quantum Hall regime under tilted magnetic fields, we can measure equilibration between both co- and counter-propagating edge channels of arbitrary filling factor ratio. We present here 4-point magnetotransport characterization of the corner junction with filling factor combinations which can all be explained using the standard Landauer-Buttiker edge channel picture. The success of this description confirms the realization of a new type of quantum Hall edge geometry.

cond-mat.mes-hall↗

arXiv2000

Spin effects in the magneto-drag between double quantum wells

We report on the selectivity to spin in a drag measurement. This selectivity to spin causes deep minima in the magneto-drag at odd fillingfactors for matched electron densities at magnetic fields and temperatures at which the bare spin energy is only one tenth of the temperature. For mismatched densities the selectivity causes a novel 1/B-periodic oscillation, such that negative minima in the drag are observed whenever the majority spins at the Fermi energies of the two-dimensional electron gasses (2DEGs) are anti-parallel, and positive maxima whenever the majority spins at the Fermi energies are parallel.

cond-mat.mes-hall↗

arXiv1999

Frictional Drag Between Coupled 2D Hole Gases in GaAs/AlGaAs Heterostructures

We report on the first measurements of the drag effect between coupled 2D-hole gases. We investigate the coupling by changing the carrier densities in the quantum wells, the widths of the barriers between the gases and the perpendicular magnetic field. From the data we are able to attribute the frictional drag to phonon coupling, because the non-parabolicity allows to tune the Fermi wavevector and the Fermi velocity separately and, thereby, to distinguish between phonon- and plasmon-dominated coupling.

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