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Heat-Driven Electron-Motion in a Nanoscale Electronic Circuit

Date : Friday, December 10th, 2021 14:00 - 15:00 Place : On Zoom (The zoom link to the seminar is displayed on the result screen after registration.) Lecturer : Dr. Shintaro Takada Affiliation : National Institute of Advanced Industrial Science and Technology (AIST) Committee Chair : Takeo Kato, Rui Sakano
e-mail: sakano@issp.u-tokyo.ac.jp

Nanoscale electronic circuits play important roles in current quantum technologies. Even when the circuits are electrically isolated, electrons in nearby circuits may interact with each other by exchanging energy and momentum. Interactions in coupled nanoscale circuits were investigated in the past with the so called drag experiment [1]. In particular, an interesting behaviour was observed when investigating adjacent but electrically isolated quantum point contacts (QPCs) that are nearly pinched [2]. When one QPC is biased with a voltage of about 1 mV or larger, a current with opposite direction is introduced in the other, unbiased QPC. As explanation of this counter-flow, asymmetric phonon-induced excitation of electrons between the two reservoirs of the drag QPC was suggested. However, a detailed understanding of the process has not been obtained yet.

In this talk, I will present our recent study investigating the interactions in a pair of neighboring one-dimensional wires, which are electrically isolated and equipped with a potential barrier at different positions, by drag-type measurements [3]. Our results corroborate the interpretation of previous experimental studies [2] and highlight the importance of geometry for the direction of the phonon-induced current. Our measurement data furthermore indicates that heat-driven electron motion is strongly affected by electron-scattering within the drive wire. Since a potential barrier is one of the key elements in quantum electronic circuits, our results will provide useful information for quantum operations in nanocircuits in particular for quantum circuits containing a potential barrier. In the end of the talk, I will also introduce the results on the induced charge in a charge-pulse injection setup rather than in a DC setup discussed above and talk about the perspectives of such a pulse setup for electron quantum optics experiments.

[1] B. N. Narozhny, and A. Levchenko, Rev. Mod. Phys. 88, 025003 (2016).
[2] V. S. Khrapai, et al., Phys. Rev. Lett. 99, 096803 (2007).
[3] S. Takada et al., J. Phys. Soc. Jpn. 90, 113707 (2021).

The zoom link to the seminar is displayed on the result screen after registration.
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(Published on: Wednesday November 24th, 2021)