Excitation of collective modes in a quantum flute

Kristinn Torfason, Andrei Manolescu, Valeriu Molodoveanu, and Vidar Gudmundsson
Phys. Rev. B 85, 245114 – Published 14 June 2012
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Abstract

We use a generalized master equation (GME) formalism to describe the nonequilibrium time-dependent transport of Coulomb interacting electrons through a short quantum wire connected to semi-infinite biased leads. The contact strength between the leads and the wire is modulated by out-of-phase time-dependent potentials that simulate a turnstile device. We explore this setup by keeping the contact with one lead at a fixed location at one end of the wire, whereas the contact with the other lead is placed on various sites along the length of the wire. We study the propagation of sinusoidal and rectangular pulses. We find that the current profiles in both leads depend not only on the shape of the pulses, but also on the position of the second contact. The current reflects standing waves created by the contact potentials, like in a wind musical instrument (for example, a flute), but occurring on the background of the equilibrium charge distribution. The number of electrons in our quantum “flute” device varies between two and three. We find that for rectangular pulses the currents in the leads may flow against the bias for short time intervals, due to the higher harmonics of the charge response. The GME is solved numerically in small time steps without resorting to the traditional Markov and rotating wave approximations. The Coulomb interaction between the electrons in the sample is included via the exact diagonalization method. The system (leads plus sample wire) is described by a lattice model.

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  • Received 2 February 2012

DOI:https://doi.org/10.1103/PhysRevB.85.245114

©2012 American Physical Society

Authors & Affiliations

Kristinn Torfason1,2, Andrei Manolescu1, Valeriu Molodoveanu3, and Vidar Gudmundsson2

  • 1School of Science and Engineering, Reykjavik University, Menntavegur 1, IS-101 Reykjavik, Iceland
  • 2Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik, Iceland
  • 3National Institute of Materials Physics, P.O. Box MG-7, Bucharest-Magurele, Romania

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Issue

Vol. 85, Iss. 24 — 15 June 2012

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