Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 24: Quantum dots and wires: Transport properties II
HL 24.1: Vortrag
Dienstag, 27. März 2007, 14:00–14:15, H15
The 0.7-anomaly in the conductance of a quantum point-contact and its interpretation in a Kondo model — •Monika Fleischer1, Daniel Schefzyk1, David Wharam1, David Ritchie2, and Michael Pepper2 — 1Institut für Angewandte Physik, Auf der Morgenstelle 10, 72076 Tübingen, Germany — 2Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, United Kingdom
Starting from the earliest transport measurements on quantum
point-contacts, the existence of a so-called “0.7-anomaly” can often be
observed in the differential conductance around 0.7·2e2/h,
in addition to the quantized steps at multiples of 2e2/h. This anomaly has
since been found to be an intrinsic feature, presumably of spin-related
origin. Still, there exists no theory to fully describe it. In a model
suggested by Cronenwett et al. [1], it is analyzed in the framework
of Kondo physics, postulating a localized spin-state in the point-contact
region at low electron densities - a possibility which
has recently been theoretically confirmed by Rejec and Meir [2]. In this talk,
measurements are presented that exhibit a distinct 0.7-anomaly in the first and
0.7-analogue in the second step as well as a zero bias anomaly in the
nonlinear data of the first step. An analysis of these characteristics in view
of the proposed Kondo model shows that in many respects, the phenomenology of
the data is well described by it, but that a number of open questions remain.
[1] S. Cronenwett et al., Phys. Rev. Lett. 88, 226805 (2002).
[2] T. Rejec and Y. Meir, Nature 442, 900 (2006).