Instituto de Ciencia de Materiales de Madrid
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Spatially resolved flow of ballistic electrons measured by quantized photocurrent spectroscopy

Klaus-Dieter Hof, Franz J. Kaiser, Markus Stallhofer, Dieter Schuh, Werner Wegscheider, Peter Hänggi, Sigmund Kohler, Jörg P. Kotthaus, and Alexander W. Holleitner
Nano Lett. 10, 3836 (2010)

Quantum point contacts (QPCs) have recently been exploited in very sensitive detection schemes to quantify the motion of cantilevers, charge and spin states in nanoscale circuits, and to monitor the coherent charge flow in two-dimensional electron gases (2DEGs). QPCs have also been utilized as electronic beam-splitters in electron interference experiments. Here, we demonstrate the use of GaAs-based QPCs to laterally resolve the ballistic flow of photo- generated electrons in a 2DEG. To this end, electron-hole pairs are optically created in a 2DEG, and the resulting current through an adjacent QPC is measured as a function of the laser spot position. The transmission of photo-generated electrons through the QPC is governed by the quantized energy and momentum values of the electron modes in the QPC. Hereby, the measured photocurrent across the QPC exhibits quantization steps. We observe that photo- generated electrons can ballistically propagate across several micrometers, before they tunnel through the QPC.

[ICMM-CSIC] [Condensed Matter Theory]
last modified: 15.3.2024 by Sigmund Kohler