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# Search results

175 records were found.

## Manifestation of a complex edge excitation structure in the fractional quantum Hall regime at high filling factors

We experimentally study equilibration across the sample edge at high fractional filling factors 4/3, 5/3 under experimental conditions, which allow us to obtain high imbalance conditions. We find a lack of the full equilibration across the edge even in the flat-band situation, where no potential barrier survives at the sample edge. We interpret this result as the manifestation of complicated edge excitation structure at high fractional filling factors 4/3, 5/3. Also, a mobility gap in the $\nu_c=1$ incompressible strip is determined in normal and tilted magnetic fields.

## Sub-linear radiation power dependence of photo-excited resistance oscillations in two-dimensional electron systems

Comment: 5 pages, 3 figures

## Cryogenic amplifier for fast real-time detection of single-electron tunneling:

The authors employ a cryogenic high electron mobility transistor (HEMT) amplifier to increase the bandwidth of a charge detection setup with a quantum point contact (QPC) charge sensor. The HEMT is operating at 1 K and the circuit has a bandwidth of 1 MHz. The noise contribution of the HEMT at high frequencies is only a few times higher than that of the QPC shot noise. The authors use this setup to monitor single-electron tunneling to and from an adjacent quantum dot. The authors measure fluctuations in the dot occupation as short as 400 ns, 20 times faster than in previous work.

## Bimodal Counting Statistics in Single Electron Tunneling through a Quantum Dot

We explore the full counting statistics of single electron tunneling through a quantum dot using a quantum point contact as non-invasive high bandwidth charge detector. The distribution of counted tunneling events is measured as a function of gate and source-drain-voltage for several consecutive electron numbers on the quantum dot. For certain configurations we observe super-Poissonian statistics for bias voltages at which excited states become accessible. The associated counting distributions interestingly show a bimodal characteristic. Analyzing the time dependence of the number of electron counts we relate this to a slow switching between different electron configurations on the quantum dot.

## Investigations on unconventional aspects in the quantum Hall regime of narrow gate defined channels

Comment: EP2DS-17 Proceedings, 6 Pages, 2 Figures

## Laterally defined freely suspended quantum dots in GaAs/AlGaAs heterostructures

Free standing beams containing a two-dimensional electron system are shaped from a GaAs/AlGaAs heterostructure. Quantum point contacts and (double) quantum dots are laterally defined using metal top gates. We investigate the electronic properties of these nanostructures by transport spectroscopy. Tunable localized electron states in freely suspended nanostructures are a promising tool to investigate the electron-phonon-interaction.

## Morphology and flexibility of graphene and few-layer graphene on various substrates

We report on detailed microscopy studies of graphene and few-layer-graphene produced by mechanical exfoliation on various semi-conducting substrates. We demonstrate the possibility to prepare and analyze graphene on (001)-GaAs, manganese p-doped (001)-GaAs and InGaAs substrates. The morphology of graphene on these substrates was investigated by scanning electron and atomic force microscopy and compared to layers on silicon oxide. It was found that graphene sheets strongly follow the texture of the sustaining substrates independent on doping, polarity or roughness. Furthermore resist residues exist on top of graphene after a lithographic step. The obtained results provide the opportunity to research the graphene-substrate interactions.

## Interaction mediated asymmetries of the quantized Hall effect

Comment: 4 pages, 3 figures

## Microwave-induced electron heating in the regime of radiation-induced magnetoresistance oscillations

Comment: 5 pages, 4 color figures

## Determination of energy scales in few-electron double quantum dots

Comment: 7 pages, 6 figures