K Klitzing

Publications (41)0 Total impact

• Source

  Available from: uni-regensburg.de

  Article: Even-Odd filling-factor switching in one-dimensional lateral superlattices

  M Tornow, Dieter Weiss, A Manolescu, R Menne, K Klitzing
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  ABSTRACT: The magnetoresistance of a two-dimensional electron system, subjected to a one- dimensional lateral potential modulation is studied for various potential amplitudes. The interplay between Landau level splitting and modulation broadening is shown to generate a transition from even to odd filling factors for the Shubnikov–de Haas resistance minima. The effect provides a tool to determine the potential amplitude. Calculations within a one-particle model agree with this evidence of the van Hove– like structure of the Landau bands.
  Physical review. B, Condensed matter 01/1997;
• Article: Evidence of Hofstadter’s Fractal Energy Spectrum in the Quantized Hall Conductance

  C. Albrecht, K Klitzing, H. Schweizer, J. H. Smet, V. Umansky, D. Weiss
• Article: Composite Fermions in Weak Periodic Potentials

  J. Smet, K Klitzing, Dieter Weiss, Werner Wegscheider
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  ABSTRACT: dc transport through one- and two- dimensional periodic modulations of density has been investigated near half filling of the lowest Landau level. For both geometries, the modulation, which is rather weak for electrons at small magnetic fields, triggers an unexpectedly strong response for composite fermions. The dramatic effect observed in 1D gratings is best described as a large positive magnetoresistance emanating from the half filled state. 2D gratings display four peaks similar to dimensional resonances observed in antidot arrays despite the small modulation amplitude.
• Article: Ballistic Motion of Electrons in a Random Magnetic Field

  P Ye, Dieter Weiss, G Lütjering, R Gerhardts, K Klitzing, K. Eberl, H Nickel, G. Weimann
• Article: Edge Channel Transport under Quantum Hall Conditions

  Dieter Weiss, S Koch, K Klitzing, H Nickel, W. Schlapp, R Lösch
• Article: Huge Magnetoresistance Oscillations in Periodic Magnetic Fields

  P Ye, Dieter Weiss, R Gerhardts, K Klitzing, S Tarucha
• Article: Novel magnetoresistance oscillations in short period 2D lateral superlattices

  C. Albrecht, J. Smet, Dieter Weiss, K Klitzing, V Umanski, H. Schweizer
• Source

  Available from: uni-regensburg.de

  Article: Magnetoresistance in a Grid-Type Lateral Superlattice: The Role of Disorder

  Dieter Weiss, A. Menschig, K Klitzing, G. Weimann
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  ABSTRACT: The magnetoresistance of a two-dimensional electron gas (2DEG) subjected to a weak two- dimensional (2D) lateral superlattice potential is expected to reflect the peculiar self-similar energy spectrum of Bloch electrons in a magnetic field, i.e., the splitting of Landau levels (LL\'s) into sublevels. One experimentally established effect of a periodic potential is that the discrete LL\'s are transformed into Landau bands and cause magnetoresistance oscillations due to an extra band- conductivity contribution. Theoretically, this band-conductivity contribution is expected to be suppressed if the splitting of the Landau bands is resolved. We study the suppression of the band-conductivity as a function of the electron mobility at millikelvin temperatures. Microfabricated gates, defined on top of high mobility GaAs/AlGaAs heterojunctions. are used to electrostatically impose a 2D-periodic potential with 150 nm period upon the 2DEG. By applying a positive bias the electron mobility is increased and we find the band- conductivity effectively suppressed if the mobility is well above 1 × 106 cm2/Vs.
• Source

  Available from: uni-regensburg.de

  Article: Novel FIR-Photodetector based on Photon Induced Interedge Channel Scattering

  D Diessel, G Müller, Dieter Weiss, K Klitzing, K Ploog, H Nickel, W. Schlapp, R Lösch
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  ABSTRACT: We demonstrate experimentally that the far- infrared photoresponse of GaAs/AlGaAs heterostructures at photon energies corresponding to cyclotron resonance absorption is strongly enhanced in the adiabatic transport regime of the quantum Hall effect (QHE). Ideal adiabatic transport is characterized within the edge channel picture of the QHE by the absence of interedge channel scattering. We realize adiabatic transport by the means of a multiple gate finger structure, which is used for a selective population of the edge channels. The cyclotron resonance absorption is interpreted as an additional interchannel scattering process increasing the magnetoresistance. Applied Physics Letters is copyrighted by The American Institute of Physics.
• Source

  Available from: uni-regensburg.de

  Article: Density of States in Landau Level Tails of GaAs-AlxGa1-xAs Heterostructures

  Dieter Weiss, E Stahl, G. Weimann, K Ploog, K Klitzing
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  ABSTRACT: From an analysis of the thermally activated resistivity as a function of the magnetic field in the quantum Hall regime we deduced the position of the Fermi energy in the mobility gap as a function of the filling factor and therefore the density of states. The measured density of states is best described by a Gaussian like profile superimposed on a constant background.
• Source

  Available from: uni-regensburg.de

  Article: Huge Photoresponse in the Nonlocal Transport Regime

  E Diessel, G Müller, Dieter Weiss, K Klitzing, K Ploog, H Nickel, W. Schlapp, R Lösch
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  ABSTRACT: We present experiments showing a significantly increased FIR photosensitivity of a high-mobility two-dimensional electron gas when transport in the quantum Hall regime is non-local, i.e. when scattering between adjacent edge channels is suppressed on macroscopic length scales. The resonant absorption under cyclotron resonance conditions enhances interedge channel scattering processes leading to a huge resistance maximum in the longitudinal resistance and to the suppression of the non- local resistance.
• Source

  Available from: uni-regensburg.de

  Article: Electrons in mesoscopically inhomogeneous magnetic fields

  P Ye, Dieter Weiss, R Gerhardts, G Lütjering, K Klitzing, H Nickel
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  ABSTRACT: We investigated the low-field magnetoresistivity of a two-dimensional electron gas (2DEG) underneath microstructured ferromagnetic gratings. The strength and the direction of an externally applied magnetic field determines the strength and the shape of the micromagnet\'s stray field. Commensurability effects due to the imposed periodic magnetic field are in competition with similar effects resulting from a strain-induced periodic electrostatic potential, associated with the patterned ferromagnets on top of the heterojunction. The presence of both a periodic magnetic field and a periodic electrostatic potential gives rise to the interesting interference phenomena presented here.
• Source

  Available from: uni-r.de

  Article: Composite Fermions in Periodic and Random Anti-Dot Lattices

  J. Smet, Dieter Weiss, K Klitzing, P Coleridge, Z. Wasilewski, R. Bergmann, H. Schweizer, A. Scherer
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  ABSTRACT: The longitudinal and Hall magnetoresistance of random and periodic arrays of artificial scatterers, imposed on a high-mobility two- dimensional electron gas, were investigated in the vicinity of Landau level filling factor í=1/2. In periodic arrays, commensurability effects between the period of the antidot array and the cyclotron radius of composite fermions are observed. In addition, the Hall resistance shows a deviation from the anticipated linear dependence, reminiscent of quenching around zero magnetic field. Both effects are absent for random antidot lattices. The relative amplitude of the geometric resonances for opposite signs of the effective magnetic field and its dependence on illumination illustrate enhanced soft wall effects for composite fermions.
• Source

  Available from: tu-bs.de

  Article: Critical Currents in quantum Hall conductors with antidot arrays

  G. Nachtwei, Z Liu, G Lütjering, R Gerhardts, Dieter Weiss, K Klitzing, K. Eberl
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  ABSTRACT: We have investigated the abrupt onset of dissipation in the quantum Hall effect (QHE) in antidot arrays patterned on a two- dimensional electron system. Different lateral configurations (periodic or aperiodic antidot arrays, and single lines of antidots, with diameters between 40 and 100 nm and periods or average spacings between 300 and 1500 nm) show remarkable differences in their non-Ohmic transport properties. In periodic arrays with large antidot diameter (lithographic diameter 100 nm), the breakdown current is systematically reduced with increasing antidot density and determined by the peak value of the local current density. From these measurements, we determined the depletion width around the antidots. In aperiodic arrays, the breakdown current is markedly lower than in periodic arrays of the same antidot size and density due to higher local values of the current density at the same total current. This was experimentally confirmed by measurements of the current dependence of the electron temperature in periodic and aperiodic arrays. Single lines of antidots, placed across the direction of current flow, cause only a small reduction of the breakdown current in comparison with unpatterned reference areas. This is in accordance with the picture of avalanche electron heating for the breakdown of the QHE, where the electrons reach a quasistationary, elevated temperature only after travel distances of several 10 ìm in a supercritical electric Hall field. In antidot lattices with very small antidot diameter (40 nm) and small lattice period (300 nm), the antidots provide additional inelastic scattering, which effectively suppresses the electron heating. This effect overcompensates the geometrical effect of the antidots and was experimentally verified by the observation of higher breakdown currents compared to the reference area. A complete absence of a hot- electron-induced hysteresis in the current- voltage characteristics was observed for this type of array.
• Source

  Available from: uni-regensburg.de

  Article: Commensurate Composite Fermions in weak periodic electrostatic potentials: Direct evidence of a periodic effective magnetic field

  J. Smet, S. Jobst, K Klitzing, Dieter Weiss, Werner Wegscheider, V. Umansky
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  ABSTRACT: Within the composite fermion model, it is anticipated that a periodic variation of the density in a two-dimensional electron system at half filling produces a periodic fictitious magnetic field. In regions of smaller density fictitious flux quanta are missing to compensate the external magnetic field. The observation of magnetic commensurability minima in the dc-transport response furnishes evidence for this fundamental aspect of the composite fermion picture. In general, composite fermions in these modulated systems behave largely equivalent to electrons moving in a periodic magnetic field.
• Article: Density of states in a two-dimensional electron gas in a strong magnetic field

  E Stahl, Dieter Weiss, G Weinmann, K Klitzing, K Ploog
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  ABSTRACT: The authors have measured the density of states in the tails of the Landau levels of GaAs-AlxGa1-xAs heterostructures by analysing the variation of the Fermi level position as a function of the magnetic field. The experimental data are best described by a gaussian-like density of states superimposed on a constant background density of states.
• Article: The Quantum Hall Effect

  H Obloh, K Klitzing, K Ploog, Dieter Weiss, E Stahl, G. Weimann
• Article: Nonlinear Quantum Transport in Antidot Arrays

  G. Nachtwei, Dieter Weiss, G Lütjering, Z Liu, K Klitzing, C Foxon, G. Weimann
• Article: Influence of Ohmic Contacts on the Amplitude of Shubnikow-de Haas Oscillations

  K Klitzing, J Nieder, R Haug, G Müller, S Koch, Dieter Weiss, K Ploog
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  ABSTRACT: The longitudinal magnetoresistance of a two- dimensional electron gas is shown to be strongly dependent on the presence of ohmic contacts between the voltage probes. By connecting or disconnecting contacts with additional gates across the potential probes it is possible to drastically change the amplitude of Shubnikov-de Haas oscillations.
• Article: Cyclotron resonance in an antidot array measured by microwave photoconductivity

  E Vasiliadou, R. Fleischmann, Dieter Weiss, D Heitmann, K Klitzing, T. Geisel, R. Bergmann, H. Schweizer, C Foxon
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  ABSTRACT: A lateral antidot array with a lattice period of 400 nm fabricated with electron- beam lithography on GaAs/AlxGa1-xAs heterostructures was investigated by microwave photoconductivity. Commensurability effects and distinct deviations from the classical cyclotron resonance have been observed in agreement with model calculations based on nonlinear dynamics of the electrons.