# Regensburg 1998 – wissenschaftliches Programm

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# TT: Tiefe Temperaturen

## TT 4: Niedrigdimensionale Systeme, Magnetotransport und Quantenhalleffekt

### TT 4.3: Vortrag

### Montag, 23. März 1998, 15:15–15:30, H 19

**Charge Fluctuations in Quantum Point Contacts and Chaotic Cavities in the Presence of Transport** — •M. H. Pedersen^{1}, M. Büttiker^{1}, and S. A. van Langen^{2} — ^{1}Département de Physique Théorique, Université de Genève, 1211 Genève 4, Switzerland — ^{2}Instituut-Lorentz, Leiden University, P.O. Box 9506, 2300 RA Leiden, The Netherlands

We analyze the frequency-dependent current fluctuations induced into a gate
near a quantum point contact or a quantum chaotic cavity.
We use a current and charge conserving, effective scattering approach
in which interactions are treated in random phase approximation.
The current fluctuations measured at a nearby gate, coupled capacitively
to the conductor, are determined by the
screened charge fluctuations of the conductor.
Both the equilibrium and the non-equilibrium current noise at the gate
can be expressed with the help of resistances
which are related to the charge dynamics on the conductor.
We evaluate these resistances for a point contact and
determine their distributions for an ensemble of chaotic
cavities. For a quantum point contact these resistances exhibit pronounced
oscillations with the opening of new channels.
For a chaotic cavity coupled to one channel point contacts
the charge relaxation resistance shows a broad distribution between
1/4 and 1/2 of a resistance quantum. The non-equilibrium resistance
exhibits a broad distribution between zero and 1/4 of a resistance
quantum.