Slow two-level systems in point contacts

Counterflow of electrons in two isolated quantum point contacts.

We study the interaction between two adjacent but electrically isolated quantum point contacts (QPCs). At high enough source-drain bias on one QPC, the drive QPC, we detect a finite electric current in the second, unbiased, detector QPC. The current generated at the detector QPC always flows in the opposite direction than the current of the drive QPC. The generated current is maximal, if the de...

Two-dimensional oscillatory patterns in semiconductors with point contacts.

Planar samples of n-GaAs with attached point contacts at different dc voltages may display a variety of spatiotemporal patterns arising from the dynamics of curved charge dipole waves. Patterns rank from oscillations due to recycling and motion of simple quasiplanar or cylindrical wave fronts to more complex patterns that include merging and splitting of different fronts. Results of numerical s...

Imaging in Quantum Point Contacts

Alessandro Cresti , Giuseppe Grosso (2) and Giuseppe Pastori Parravicini (3) (1) NEST-INFM, Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy, and Dipartimento di Fisica E. Fermi, Largo B. Pontecorvo 3, I-56127 Pisa, Italy [email protected] (2) NEST-INFM and Dipartimento di Fisica E. Fermi, Largo B. Pontecorvo 3, I-56127 Pisa, Italy (3) NEST-INFM and Dipartimento di Fisica ...

Localized plasmons in point contacts

Using a hydrodynamic model of the electron fluid in a point contact geometry we show that localized plasmons are likely to exist near the constriction. We attempt to relate these plasmons with the recent experimental observation of deviations of the quantum point contact conductance from ideal integer quantization. As a function of temperature this deviation exhibits an activated behavior, exp(...

Aluminum break-point contacts