Excitation of collective modes in a quantum flute

Physical review. B, Condensed matter (Impact Factor: 3.77). 02/2012; 85(24). DOI: 10.1103/PhysRevB.85.245114
Source: arXiv

ABSTRACT We use a generalized master equation (GME) formalism to describe the
non-equilibrium 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 which 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.

  • [Show abstract] [Hide abstract]
    ABSTRACT: A narrowband terahertz signal generated by a unitravelling carrier photodiode (UTC-PD) interfaced with a dual-mode Fabry-P\'{e}rot laser diode is demonstrated. A beat tone corresponding to the free spectral range is generated on the UTC-PD, and radiated by a transverse-electromagnetic-horn antenna. A terahertz signal at a frequency of 372 GHz, featuring a linewidth of 17 MHz is recorded by a subharmonic mixer coupled to an electrical spectrum analyzer. All components involved in this experiment operate at room temperature. The linewidth and the frequency of the emitted terahertz wave are analyzed, along with their dependency on DC-bias conditions applied to laser diode.
    Applied Physics Letters 01/2010; 96:241106. · 3.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A quantized current in a lateral quantum dot, defined by metal gates in the two-dimensional electron gas (2DEG) of a GaAs/AlGaAs heterostructure, was observed. By modulating the tunnel barriers in the 2DEG with two phase-shifted RF signals and employing the Coulomb blockade of electron tunneling, quantized current plateaus in the current-voltage characteristics were produced at integer multiples of ef, where f is the RF frequency. This demonstrates that an integer number of electrons pass through the quantum dot each RF cycle.
    Physical Review Letters 10/1991; 67(12):1626-1629. · 7.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present numerical results of an examination of the current mirror effect in a single-electron turnstile capacitively coupled to a one-dimensional (1D) array of small tunnel junctions. We deal with a 20-junction 1D array and 4-junction turnstile coupled at their center electrodes via a coupling capacitor. A coupling parameter, Qc, and a current mirror index are introduced to define the strength of coupling and to evaluate the quality of the current mirror effect, respectively. Numerical results show that a finite gate charge of e/2 to the center electrodes of both the 1D array and the turnstile enhances the current mirror effect, where −e is the charge of an electron. To investigate the enhanced current mirror effect, charge propagation in the 1D array under a finite gate charge of e/2 is simulated. It is found that electrons temporarily trapped at the center electrode in the 1D array play an important role in the enhancement of the current mirror effect. © 2003 American Institute of Physics.
    Journal of Applied Physics 09/2003; 94(7):4480-4484. · 2.21 Impact Factor


Available from