Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 53: Transport: Topological Insulators 3 (jointly with TT, MA)

HL 53.7: Vortrag

Mittwoch, 28. März 2012, 11:00–11:15, BH 334

Bloch–Zener Oscillations in Graphene and Topological Insulators — •Viktor Krueckl and Klaus Richter — Institut für Theoretische Physik, Universität Regensburg, Germany

Conventional free electrons in a superlattice subject to an accelerating drift potential feature a periodic motion known as Bloch oscillations. This physical phenomenon is enriched for topological insulators and graphene, since the electronic structure of those materials close to the Fermi energy is governed by a linear dispersion with a vanishing bandgap between electron and hole states. As a consequence superlattices based on zero-gap semiconductors exhibit characteristic Bloch–Zener oscillations that emerge from the coherent superposition of Bloch oscillations and multiple Zener tunneling between the electron and hole branch [1]. We demonstrate this mechanism by means of wave packet dynamics in various spatially periodically modulated nanoribbons subject to an external bias field. The associated Bloch frequencies exhibit a peculiar periodic bias dependence which we explain within a two-band model. Supported by extensive numerical transport calculations, we show that this effect gives rise to distinct current oscillations observable in the I-V characteristics of graphene and mercury telluride superlattices.

[1] Viktor Krueckl and Klaus Richter, arXiv:1109.5541v1 (2011)