Hamburg 2001 – scientific programme

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TT: Tiefe Temperaturen

TT 8: Mesoskopische Systeme

TT 8.5: Talk

Tuesday, March 27, 2001, 11:15–11:30, A

Conductance Sum Rule in Atomic Break Junctions — •Stefan Kirchner, Johann Kroha, and Peter Wölfle — Institut fuer Theorie der Kondensierten Materie, Universität Karlsruhe

In recent experiments on nanoscale break junctions E. Scheer et al. [PRL 78, 3535 (1997)] were able to show that the conductance of the junction is determined by the atomic orbitals. Surprisingly, in several materials the total conductance is almost quantized although the transmission of each channel shows a strong variation while the junction is elongated.
We argue that the low energy behavior of nanoscale break junctions can be described by a multi-level Anderson impurity model. For this model we derive a generalization of the unitarity sum rule to multiple transmission channels. This approximate sum rule offers an explanation for the quasi-quantization of the conductance observed in experiments.