Mechanical modulation of single-electron tunneling through molecular-assembled metallic nanoparticles

We present a microscopic study of single-electron tunneling in nanomechanical double-barrier tunneling junctions formed using a vibrating scanning nanoprobe and a metallic nanoparticle connected to a metallic substrate through a molecular bridge. We analyze the motion of single electrons on and off the nanoparticle through the tunneling current, the displacement current and the charging-induced electrostatic force on the vibrating nanoprobe. We demonstrate the mechanical single-electron turnstile effect by applying the theory to a gold nanoparticle connected to the gold substrate through alkane dithiol molecular bridge and probed by a vibrating platinum tip.Comment: Accepted by Phys. Rev.

Current driven switching of magnetic layers

The switching of magnetic layers is studied under the action of a spin current in a ferromagnetic metal/non-magnetic metal/ferromagnetic metal spin valve. We find that the main contribution to the switching comes from the non-equilibrium exchange interaction between the ferromagnetic layers. This interaction defines the magnetic configuration of the layers with minimum energy and establishes the threshold for a critical switching current. Depending on the direction of the critical current, the interaction changes sign and a given magnetic configuration becomes unstable. To model the time dependence of the switching process, we derive a set of coupled Landau-Lifshitz equations for the ferromagnetic layers. Higher order terms in the non-equilibrium exchange coupling allow the system to evolve to its steady-state configuration.Comment: 8 pages, 2 figure. Submitted to Phys. Rev.

Indirect Exchange Interaction between two Quantum Dots in an Aharonov-Bohm Ring

We investigate the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between two spins located at two quantum dots embedded in an Aharonov-Bohm (AB) ring. In such a system the RKKY interaction, which oscillates as a function of the distance between two local spins, is affected by the flux. For the case of the ferromagnetic RKKY interaction, we find that the amplitude of AB oscillations is enhanced by the Kondo correlations and an additional maximum appears at half flux, where the interaction is switched off. For the case of the antiferromagnetic RKKY interaction, we find that the phase of AB oscillations is shifted by pi, which is attributed to the formation of a singlet state between two spins for the flux value close to integer value of flux.Comment: 10 pages, 5 figure

Carbon Nanotubes as Nanoelectromechanical Systems

We theoretically study the interplay between electrical and mechanical properties of suspended, doubly clamped carbon nanotubes in which charging effects dominate. In this geometry, the capacitance between the nanotube and the gate(s) depends on the distance between them. This dependence modifies the usual Coulomb models and we show that it needs to be incorporated to capture the physics of the problem correctly. We find that the tube position changes in discrete steps every time an electron tunnels onto it. Edges of Coulomb diamonds acquire a (small) curvature. We also show that bistability in the tube position occurs and that tunneling of an electron onto the tube drastically modifies the quantized eigenmodes of the tube. Experimental verification of these predictions is possible in suspended tubes of sub-micron length.Comment: 8 pages, 5 eps figures included. Major changes; new material adde

Twisted exchange interaction between localized spins embedded in a one- or two-dimensional electron gas with Rashba spin-orbit coupling

We study theoretically the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in one- and two-dimensions in presence of a Rashba spin-orbit (SO) coupling. We show that rotation of the spin of conduction electrons due to SO coupling causes a twisted RKKY interaction between localized spins which consists of three different terms: Heisenberg, Dzyaloshinsky-Moriya, and Ising interactions. We also show that the effective spin Hamiltonian reduces to the usual RKKY interaction Hamiltonian in the twisted spin space where the spin quantization axis of one localized spin is rotated.Comment: 4pages, no figur

Steering of a Bosonic Mode with a Double Quantum Dot

We investigate the transport and coherence properties of a double quantum dot coupled to a single damped boson mode. Our numerically results reveal how the properties of the boson distribution can be steered by altering parameters of the electronic system such as the energy difference between the dots. Quadrature amplitude variances and the Wigner function are employed to illustrate how the state of the boson mode can be controlled by a stationary electron current through the dots.Comment: 10 pages, 6 figures, to appear in Phys. Rev.

Transport via a quantum shuttle

Published versio

Weighted two-particle Green's functions in the coherent-potential approximation and perturbation effects in tunneling systems out of equilibrium

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