[{"type":"speech","title":"One dimensional organometallic wires: electronic structure and transport properties","issued":{"date-parts":[["2007"]]},"author":[{"family":"Maslyuk","given":"V."},{"family":"Bagrets","given":"A."},{"family":"Brandbyge","given":"M."},{"family":"Mertig","given":"I."}],"note":"71.Jahrestagung der Deutschen Physikalischen Gesellschaft und DPG Fr\u00fchjahrstagung des Arbeitskreises Festk\u00f6rperphysik, Fachverband Tiefe Temperaturen, Regensburg, 26.-30.M\u00e4rz 2007 Verhandlungen der Deutschen Physikalischen Gesellschaft, R.6, B.42(2007) TT 6.9","abstract":"Section Low Temperature Physics (TT)\nMonday\nInstitute of Technology (EPFL), CH-1015 Lausanne, Switzerland\nWe performed low temperature measurements of magnetoconductance\nand non linear conductance for multiwall carbon nanotubes. Signatures of phase coherent di\ufb00usive transport are the weak localization\ndip and universal conductance \ufb02uctuations. At very low temperature,\n\u201danomalous\u201d Coulomb blockade is observed: we \ufb01nd a superposition\nof several diamonds patterns in the Vsd-Ugate plane with di\ufb00erent\nsize. The stability diagrams are more regular than in previous studies, but qualitatively di\ufb00erent from that observed in single wall carbon\nnanotubes. We attribute this behavior to the e\ufb00ect of the inner shells\non the charging process and propose a model where the nanotube is\nrepresented by two quantum dots in parallel.\nTT 6.9\nMon 16:15\nH19\nand transport properties \u2014 \u2022Volodymyr Maslyuk1 , Alexei\nBagrets2 , Mads Brandbyge3 , and Ingrid Mertig1 \u2014 1 MartinLuther-Universit\u00a8t Halle-Wittenberg, Physical Department, Halle,\nGermany \u2014 2 Institute of Nanotechnology, Forschungszentrum Karlsruhe, Germany \u2014 3 NanoDTU, MIC-Department of Micro and Nanotechnology, Technical University of Denmark, Lyngby, Denmark\nDuring the last years, organometallic systems have attracted increasing\nattention. The small size of the molecules and the spin degree of freedom allow us to consider them as independent logic units and think\nabout new electronic devices with unforeseen properties. Here, we\nfocus on multi-decker metal-cyclopentadienyl Met(C5H5) and metalbenzene Met(C6H6) molecules. Recently, we have predicted that a\none-dimensional vanadium-benzene wire is a half-metallic ferromagnet\nand \ufb01nite V(C6H6) clusters coupled to magnetic leads are working as\nspin-\ufb01lter [1]. Moreover, our bias dependence calculations show conservation of the half-metallic properties in a wide voltage window. Using density functional theory and the non-equilibrium Green\u2019s-function\nmethod, implemented in the TranSIESTA code [2], we have investigated the electronic and transport properties of 1D organometallic\nwires coupled with Co(100) electrodes. We have also investigated the\nelectron transport through the molecules in the case of antiparallel\nmagnetic con\ufb01guration of the electrodes and predict an impressive\nmagnetoresistance e\ufb00ect. [1] V. Maslyuk et al., Phys. Rev. Lett\n97, 097201 (2006). [2] M. Brandbyge et al. Phys. Rev. B 65, 165401\n(2002).\nTT 6.10\nMon 16:30\nH19\nCotunneling and non-equilibrium magnetization in magnetic\nmolecular monolayers \u2014 \u2022Florian Elste1 and Carsten Timm2 \u2014\n1 Institut f\u00a8 r Theoretische Physik, Freie Universit\u00a8t Berlin, Germany\n\u2014 2 Department of Physics and Astronomy, University of Kansas, USA\nWe study the interplay of electronic transport through monolayers of\nmagnetic molecules and their non-equilibrium magnetic moment. A\nmaster-equation approach going beyond the sequential-tunneling approximation is applied to study the Coulomb-blockade regime. While\nthe current is very small in this case, the magnetization can be switched\nby an amount of the order of the saturation magnetization by a small\nchange of bias voltage, and without causing the \ufb02ow of a large current.\nInelastic cotunneling processes manifest themselves as steps in the differential conductance, which are accompanied by much larger changes\nin the magnetization. In addition, the magnetization in the Coulombblockade regime exhibits strong signatures of sequential-tunneling processes de-exciting molecular states populated by inelastic cotunneling.\nWe also consider the case of a magnetic single-molecule transistor,\n\ufb01nding that cotunneling processes lead to the occurrence of magnetic\nsidebands below the Coulomb-blockade threshold. In the context of\nspintronics applications, we investigate e\ufb00ects of additional spin relaxation. Our results show that su\ufb03ciently fast spin relaxation washes\nout the \ufb01ne structure in the di\ufb00erential conductance and in the magnetization. At the same time, fast spin relaxation, while in general\nundesirable, can lead to a highly-polarized current in the presence of\na magnetic \ufb01eld.\nTT 6.11\nMon 16:45\nH19\nFU Berlin, Arnimallee 14, 14195 Berlin\nTT 7: Quantum Coherence and Quantum Information Systems II\nTime: Monday 14:00\u201316:00\nLocation: H20\nTT 7.1\nMon 14:00\nH20\nUse of dynamical coupling for improved quantum state transfer \u2014 \u2022Andriy Lyakhov and Christoph Bruder \u2014 University of\nE\ufb03cient short-distance quantum state transfer is an important problem in quantum information processing. One of the most promising\nsolutions is to use chains constructed from qubits that are statically\ncoupled to each other [1]. Here, we propose a method to improve quantum state transfer in such transmission lines. The idea is to localize\nthe information on the last qubit of a transmission line by dynamically varying the coupling constants between the \ufb01rst and the last pair\nof qubits. We also show that this method increases the \ufb01delity of the\nstate transfer and that this e\ufb00ect is stable to static disorder in the coupling constants and dynamical \ufb02uctuations in the coupling\/decoupling\nfunctions [2].\n[1] S. Bose, Phys. Rev. Lett. 91 207901 (2003)\n[2] A. O. Lyakhov and C. Bruder, Phys. Rev. B 74, 235303 (2006)\nTT 7.2\nMon 14:15\nH20\nA 2D array of Cooper pair boxes as a candidate for a pro\u00a8\ntected qubit \u2014 \u2022Jorg-Hendrik Bach, Alexander Shnirman, and\n\u00a8\nGerd Schon \u2014 Institut f\u00a8r theoretische Festk\u00a8rperphysik, Universit\u00a8t\nWe consider a 2-dimensional array of double-island Cooper pair boxes\nas a candidate for a protected qubit. Two types of couplings are implemented in the array. These are inductive nearest-neighbour cou-\nplings along the array\u2019s rows and capacitive nearest-neighbour couplings between the array\u2019s columns. Projected onto the doubly degenerate ground states of the Cooper pair boxes the two couplings do\nnot commute. Thus the system reduces e\ufb00ectively to an array of spin1\/2 particles with non-commuting row- and column couplings. This\nreminds of the system proposed by Doucot et al. [Phys. Rev. B 71,\n024505 (2005)] in the context of protected quantum computing. Similarities and di\ufb00erences to this system are pointed out; furthermore,\nthe in\ufb02uence of the third level of the Cooper pair box is investigated.\nTT 7.3\nMon 14:30\nH20\nMacroscopic quantum tunneling in globally coupled series arrays of Josephson junctions \u2014 \u2022Mikhail V. Fistul \u2014 Theoretische Physik III, Ruhr-Universit\u00a8t Bochum, D-44801, Bochum Germany\nA quantitative analysis of an escape rate for switching from the superconducting state to a resistive one in series arrays of globally coupled\nJosephson junctions will be presented. A global coupling is provided\nby an external shunting impedance. Such an impedance can strongly\nsuppress both the crossover temperature from the thermal \ufb02uctuation\nto quantum regimes, and the macroscopic quantum tunneling (MQT)\nin short Josephson junction series arrays [1]. However, in large series\narrays we obtain an enhancement of the crossover temperature, and\na giant increase of the MQT es","kit-publication-id":"230067478"}]