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HL: Fachverband Halbleiterphysik

HL 71: Transport Properties

HL 71.7: Vortrag

Donnerstag, 23. März 2017, 11:15–11:30, POT 112

Gaussian beam electron optics with quantum point contacts — •Jaan Freudenfeld¹, Sergey Platonov^1,2, Max Geier³, Piet Brouwer³, Vladimir Umansky⁴, and Stefan Ludwig¹ — ¹Paul-Drude-Institut für Festkörperelektronik, Berlin, Deutschland — ²Ludwig-Maximilians-Universität, München, Deutschland — ³Freie Universität, Berlin, Deutschland — ⁴Weizmann Institute of Science, Tel Aviv, Israel

Precise control of the motion of ballistic electrons on the nanoscale would be a major step towards the realization of integrated electronic quantum circuits. Quantum point contacts (QPCs) are fundamental building blocks of nanoscale circuits and characterized by quantized conductance. The emission of electrons from these one-dimensional constrictions happens within an aperture angle and is subject to diffraction. We experimentally study the diffraction pattern of QPCs with confinement potentials resembling parabolic saddle point potentials. In contrast to usual hard wall single slit experiments our parabolic "slits" emit electrons in Hermite functions. As a consequence the ballistic electron dynamics is described by Gaussian beam electron optics yielding a very different diffraction pattern compared to the usual single slit plane wave approach. We experimentally explore the diffraction pattern by combining magnetic deflection with electrostatic focusing using a field effect lens and compare the results with model calculations. The observed diffraction pattern and focusing properties of our electrostatic lens clearly indicate Gaussian beam electron optics, a crucial information for the design of future quantum circuit applications.