[{"type":"speech","title":"Cross-correlations in transport through two parallel quantum dots","issued":{"date-parts":[["2008"]]},"author":[{"family":"Haupt","given":"S."},{"family":"Aghassi","given":"J."},{"family":"Hettler","given":"M."},{"family":"Sch\u00f6n","given":"G."}],"note":"72.Jahrestagung der Deutschen Physikalischen Gesellschaft und DPG Fr\u00fchjahrstagung des Arbeitskreises Festk\u00f6rperphysik, Fachverband Tiefe Temperaturen, Berlin, 25.-29.Februar 2008 Verhandlungen der Deutschen Physikalischen Gesellschaft, R.6, B.43(2008) TT 20.5 6th Rencontres de Moriond in Mesoscopic Physics, La Thuile, I, March 8-15, 2008","abstract":"Low Temperature Physics Division (TT)\nTuesday\nsit\u00a8t Stuttgart \u2014 4 Institut f\u00a8 r Theoretische Physik, Georg-Augusta\nChemie JWG-Universit\u00a8t Frankfurt; SFB\/TRR49\nA quantum critical point (QCP) is found in systems where a phase\ntransition at T = 0 is driven by an external control parameter. Although a QCP takes place at T = 0, inaccessible by experiment, it\nhas a signi\ufb01cant in\ufb02uence on the physical properties over a wide range\nof temperature. Here we concentrate on \ufb01eld-induced QCPs in lowdimensional molecule-based spin systems. The molecular approach\nenables us to generate materials with magnetic exchange coupling constants weak enough for laboratory \ufb01elds to drive the system into a new\nground state. We present data of the magnetocaloric e\ufb00ect across the\nsaturation \ufb01eld of an antiferromagnetic S = 1\/2 Heisenberg chain system. These results compare favourably with theoretical predictions. In\nadditon, we report thermodynamic measurements on the \ufb01eld-induced\nmagnetic transition in coupled S = 1\/2 dimer systems.\nTT 19.16\nTue 18:15\nQuantum critical scaling behavior of decon\ufb01ned spinons\n\u2014 \u2022Flavio Nogueira1 , Steinar Kragset2 , and Asle Sudbo2 \u2014\n1 Institut f\u00a8 r Theoretische Physik, Freie Universit\u00a8t Berlin, Arnimallee\n14, D-14195 Berlin \u2014 2 Department of Physics, Norwegian University\nof Science and Technology, N-7491 Trondheim, Norway\nWe perform a renormalization group analysis of some important effective \ufb01eld theoretic models for decon\ufb01ned spinons. We show that\ndecon\ufb01ned spinons are critical for an isotropic SU(N) Heisenberg antiferromagnet, if N is large enough. We argue that nonperturbatively\nthis result should persist down to N = 2 and provide further evidence\nfor the so called decon\ufb01ned quantum criticality scenario. Decon\ufb01ned\nspinons are also shown to be critical for the case describing a transition\nbetween quantum spin nematic and dimerized phases. On the other\nhand, the decon\ufb01ned quantum criticality scenario is shown to fail for\na class of easy-plane models. For the cases where decon\ufb01ned quantum\ncriticality occurs, we calculate the critical exponent \u03b7 for the decay of\nthe two-spin correlation function to \ufb01rst-order in = 4 \u2212 d.\nH 3010\nTT 20: Transport: Nanoelectronics I - Quantum Dots, Wires, Point Contacts 1\nTime: Tuesday 14:00\u201315:30\nInvited Talk\nLocation: EB 202\nTT 20.1\nTue 14:00\nEB 202\nAdiabatic pumping in nanostructures \u2014 \u2022Michele Governale\nA DC current can be driven through a mesoscopic conductor in the absence of an applied transport voltage by changing periodically in time\nsome of the properties of the conductor. This transport mechanism\nis known as pumping. If the time-dependent parameters vary slowly\nas compared to the characteristic internal time scales of the system,\npumping is adiabatic, and the average transmitted charge per cycle\ndepends only on the area of the cycle but not on its detailed timing.\nIn this talk we present the main theoretical concepts in the \ufb01eld and\ndescribe some recent developments, such as pumping trough interacting systems [1,2] and in hybrid superconducting-normal structures [3].\n[1] J. Splettstoesser, M. Governale, J. K\u00a8nig, and R. Fazio, Phys.\nRev. Lett. 95, 246803 (2005).\n[2] J. Splettstoesser, M. Governale, J. K\u00a8nig, and R. Fazio, Phys.\nRev. B 74, 085305 (2006).\n[3] M. Governale, F. Taddei, R. Fazio, and F. W. J. Hekking, Phys.\nRev. Lett. 95, 256801 (2005).\nTT 20.2\nTue 14:30\nEB 202\nCooper pair pumping in presence of dissipation \u2014 \u2022Valentina\nBrosco1 , Alexander Shnirman1,2 , Rosario Fazio3,4 , and Gerd\n\u00a8\nSchon1 \u2014 1 Institut f\u00a8r Theoretische Festk\u00a8rperphysik and DFG Cenu\nter for Functional Nanostructures (CFN), Universit\u00a8t Karlsruhe, Karla\nsruhe, Germany \u2014 2 Institut f\u00a8 r Theoretische Physik, Universit\u00a8t Innsu\nbruck, Innsbruck, Austria \u2014 3 International School for Advanced Studies (SISSA), Trieste, Italy \u2014 4 NEST-CNR-INFM and Scuola Normale\nSuperiore, Pisa, Italy\nIn a Cooper pair pump charge transport is obtained via an adiabatic\nand periodic manipulation of Josephson couplings or gate voltages and\nit is a coherent process. Several works investigated the connection between Cooper pair pumping and the geometric and topological properties of the pumping cycle in the parameters space [1]. Recently\nthe predicted relation between Berry\u2019s phase and pumped charge was\ndemonstrated experimentally [2]. In the present work we analyze the\ne\ufb00ects of noise on Cooper pair pumping and we show that dissipation\nmay induce a new geometric contribution in the transferred charge. We\nshow that this contribution can be experimentally distinguished both\nfrom the usual pumped charge and from the supercurrent contribution\nand we propose an experiment where the theory can be probed.\n[1] M. Aunola and J. J. Toppari, Phys. Rev. B 68, 020502 (2003); V.\nBrosco, R. Fazio, F. W. J. Hekking, and A. Joye, cond-mat\/0702333.\n[3] M.Mottonen, J. J. Vartiainen, and J. P. Pekola, condmat\/0710.5623.\nUniversit\u00a8t Bochum, 44780 Bochum, Germany\nWe study adiabatic pumping in Aharonov-Bohm interferometers,\nwhere a quantum dot is embedded in one or in both arms. Charge\npumping occurs if two parameters are changed periodically in time.\nThe limit of small frequencies de\ufb01nes the adiabatic regime.\nFor our calculations we use a real-time diagrammatic technique and\ncombine the properties of AB interferometers [1] with the properties\nof adiabatic pumping [2] for dots with strong Coulomb interaction.\nBy performing a perturbation expansion in the pumping frequency\nand in the tunnel-coupling strength we calculate the magnetic-\ufb02ux dependence of the pumped charge and compare it with the results for\nrecti\ufb01cation of an AC voltage, which may yield an e\ufb00ective DC current\nas well.\nWe get information about the character of adiabatic pumping, which\ncould be interpreted as peristaltic, but phase-coherent. Furthermore\nwe \ufb01nd, that adiabatic pumping and recti\ufb01cation show di\ufb00erent symmetries and, thereby, are distinguishable.\n[1]J. K\u00a8nig and Y. Gefen, Phys. Rev. B 65, 045316 (2002).\n[2]J. Splettstoesser, M. Governale, J. K\u00a8nig, and R. Fazio, Phys.\nRev. B 74, 085305 (2006).\nTT 20.4\nTue 15:00\nEB 202\nNon-local Andreev re\ufb02ection in quantum dots \u2014 \u2022David Fut\u00a8\n\u00a8\nterer, Michele Governale, and Jurgen Konig \u2014 Institut f\u00a8 r Theu\nmany\nWe consider a single-level quantum dot attached to one superconducting and two ferromagnetic leads. The transport through this system\nis in\ufb02uenced by the interplay of proximity e\ufb00ect, spin accumulation,\nCoulomb interaction and non-equilibrium due to \ufb01nite bias voltage.\nWe employ a real-time diagrammatic technique that accounts for\ncoupling both to ferromagnetic[1] and superconducting[2] leads. We\nperform a systematic expansion in the tunnel-couplings to the leads.\nIn the limit of large superconducting gap, all orders in the tunnelcoupling strength with the superconductor can be resummed. We calculate the transport properties of the system and identify schemes for\ndetection of non-local Andreev re\ufb02ection.\n[1] M. Braun, J. K\u00a8nig, and J. Martinek, Phys. Rev. B 70, 195345\n(2004)\n[2] M. G. Pala, M. Governale, and J. K\u00a8nig, New J. Phys. 9, 278\n(2007)\nTT 20.5\nTue 15:15\nEB 202\nEB 202\nCross-Correlations in transport through two parallel quantum dots \u2014 \u2022Sebastian Haupt1,2 , Jasmin Aghassi1 , Matthias\n\u00a8\nHettler2 , and Gerd Schon1,2 \u2014 1 Institut f\u00a8 r theoretisu\nche Festk\u00a8rperphysik, Universit\u00a8t Karlsruhe, 76218 Karlsruhe \u2014\nAdiabatic pumping in a quantum dot-Aharonov-Bohm interferometer \u2014 \u2022Bastian Hiltscher, Michele Governale, and\n\u00a8\n\u00a8\nWe study cross-correlations of currents through two parallel quantum\ndots coupled to four independent electrodes. The quantum dots are\ncoupled by intra-dot Coulomb interactions bu","kit-publication-id":"230071121"}]