Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 87: Poster: Topological Insulators (HL jointly with MA, O)

O 87.1: Poster

Thursday, April 3, 2014, 17:00–20:00, P1

Theoretical description of scanning gate microscopy on quantum Hall point contacts — •Martin Treffkorn and Bernd Rosenow — Institut für theoretische Physik, Universität Leipzig, Germany

In the integer quantum Hall regime, the concept of edge states allows to describe dissipationless, one-dimensional transport along the boundary of a sample. Recent experimental progress in the application of low-temperature scan-gate microscopy has allowed to image the spatial structure of edge states with high resolution [1]. To this end, a negatively charged scanning tip approaches a quantum point contact (QPC), such that changes in the spatial edge structure can be measured in the differential resistance of the QPC. The resistance only change when the tip induced change in electron density prevents an edge channel from passing through the point contact, since electrons may only travel along the quasi one dimensional channels at the edge. From the differential change of resistance versus the tip position one obtains a picture of the edge channels that are present in the system. We use a recursive Greens function algorithm to calculate the conductance of a QPC in the presence of a scanning tip. In our calculations we consider the existence of alternating compressible and incompressible strips across the system, paying particular attention to the influence of Coulomb interactions on the edge structure.

[1] N. Pascher, C. Rössler, T. Ihn, K. Ensslin, C. Reichl, and W. Wegscheider, arXiv:1309.4918 (2013).