# Dresden 2014 – wissenschaftliches Programm

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# HL: Fachverband Halbleiterphysik

## HL 30: Poster: Quantum dots and wires: Preparation, characterization, optical properties and transport

### HL 30.7: Poster

### Montag, 31. März 2014, 17:00–20:00, P2

**Indirect exchange interaction between quantum dots in a magnetic field** — •Alexander W. Heine^{1}, Katharina Janzen^{2}, Gertrud Zwicknagl^{2}, and Rolf J. Haug^{1} — ^{1}Institut für Festkörperphysik, Leibniz Universität Hannover, 30167 Hannover, Germany — ^{2}Institut für Mathematische Physik, Technische Universität Braunschweig, 38106 Braunschweig, Germany

Quantum dots with an odd number of electrons have a non-zero spin which is a possible realization of a qubit in quantum information processes. An indirect exchange interaction between magnetic moments, the so-called Ruderman-Kittel-Kasuya-Yosida interaction, is a possible mechanism to control this spin qubit.

We investigate the exchange constant J of two localized moments mediated by the electrons in a large circular quantum dot in a perpendicular magnetic field. Our results for the effective interaction show signatures known for both, the exchange couplings in metals and in molecules. This is consistent with the fact, that the quantum dot is intermediate between a large molecule and a metal.

A second effect observed for the localized spin of a quantum dot is the Kondo effect. In our system of two quantum dots separated by an open conducting region the Kondo effect can be used as a spectroscopic tool to demonstrate the presence of the indirect exchange interaction. Measurements are performed in a temperature range of 25 mK to 900 mK. A high perpendicular magnetic field up to 5.5 T is applied. The temperature dependence of the differential conductance is analyzed for varying magnetic field.