Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 12: Transport: Nanoelectronics I - Quantum Dots, Wires, Point Contacts 2
TT 12.1: Vortrag
Montag, 26. März 2012, 15:00–15:15, BH 334
Mesoscopic Stoner instability in metallic nanoparticles revealed by shot noise — •Björn Sothmann1, Jürgen König2, and Yuval Gefen3 — 1Département de Physique Théorique, Université de Genève — 2Theoretische Physik, Universität Duisburg-Essen — 3Dept. of Condensed Matter Physics, Weizmann Institute of Science
The interplay between discrete level spacing and exchange interactions of electron spins in metallic nanoparticles leads to the so called mesoscopic Stoner instability. The nanoparticle becomes partially polarized and its spin depends on the ratio of exchange coupling and level spacing.
We study sequential tunneling through a metallic nanoparticle close to the Stoner instability coupled to parallely magnetized electrodes. Transport channels associated with the excitations of the nanoparticle’s total spin open up when increasing the bias voltage. This leads to a steplike increase of the current. The Fano factor, in contrast, shows oscillations between large super-Poissonian and sub-Poissonian values as a function of voltage. We explain the enhanced Fano factor in terms of generalized random-telegraph noise and propose the shot noise as a convenient and robust tool to probe the mesoscopic Stoner instability.
B. Sothmann, J. König, Y. Gefen, arXiv:1110.2589v2.