Browsing by Subject "Drag effect"

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    Collective modes in a bilayer dipolar fermi gas and the dissipationless drag effect
    (Springer, 2013) Tanatar, Bilal
    We consider the collective modes of a bilayer dipolar Fermi system in which the particles interact via long range (∼1/r 3) interaction. Assuming that each layer has a background flow which varies little and that the dynamics of the superfluid near T=0 is the same as that of a normal fluid, we obtain the dispersion relations for the collective modes in the presence of background flow. Decomposing the background flow into two parts, the center-of-mass flow and counterflow, we focus on the properties of the counterflow. We first find an estimate of the change in the zero-point energy ΔE ZP due to counterflow for a unit area of bilayer. Combining this with the free energy F of the system and taking the partial derivatives with respect to background velocities in the layers, we determine the current densities which reveal the fact that current in one layer does not only depend on the velocity in the same layer but also on the velocity of the other layer. This is the drag effect and we calculate the drag coefficient.
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    Current enhancement and negative differential conductance in parallel quantum dot systems
    (American Institute of Physics, 2011) Tanatar, Bilal; Moldoveanu V.
    We present calculations on the transport properties of a double quantum dot (DQD) capacitively coupled to another individually biased dot. The effects of the intradot and interdot Coulomb interaction are included within the random-phase approximation (RPA) implemented in the Keldysh formalism. We show that by increasing the bias on the nearby dot the inelastic Coulomb scattering modifies the current in the double dot. The sign of the current depends on the detuning of the double dot levels and intradot transitions lead to negative differential conductance. The enhancement of the current due to the energy quanta transferred from the strongly biased dot suggests a quantum ratchet or Coulomb drag mechanism. © 2011 American Institute of Physics.
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    Plasmons and the drag effect in a strong magnetic field
    (Elsevier B.V., 2002) Manolescu, A.; Tanatar, Bilal
    We study the effect of magnetoplasmons on the drag resistance in a strong magnetic field, at finite temperatures. The typical magnetic field is about 1 T, and the temperature is up to 10 K. The Landau levels are broadened by disorder, but well separated in energy. We discuss intra-Landau level magnetoplasmons, with low frequencies, below ωc, and inter-Landau level magnetoplasmons (also called Bernstein modes), with high frequencies, close to multiples of ωc. We compare the temperature dependence of the minima and maxima of the Shubnikov-de Haas oscillations of the transresistance.