[{"type":"speech","title":"Scanning probe measurements and electromigration of metallic nanostructures under ultra-high vacuum conditions","issued":{"date-parts":[["2009"]]},"author":[{"family":"St\u00f6ffler","given":"D."},{"family":"Fostner","given":"S."},{"family":"L\u00f6hneysen","given":"H. von"},{"family":"Gr\u00fctter","given":"P."},{"family":"Hoffmann","given":"R."}],"note":"Fr\u00fchjahrstagung DPG, Fachverband Tiefe Temperaturen, Dresden, 22.-27.M\u00e4rz 2009 Verhandlungen der Deutschen Physikalischen Gesellschaft, R.6, B.44(2009) TT 2.2","abstract":"Low Temperature Physics Division (TT)\nMonday\nTT 2: Transport: Nanoelectronics I - Quantum Dots and Wires, Point Contacts 1\nTime: Monday 10:15\u201313:00\nLocation: HSZ 301\nTT 2.1\nMon 10:15\nHSZ 301\nFriedel oscillations in quantum wires: interplay of interactions and non-equilibrium \u2014 Daniel F Urban1 and \u2022Andreas\nWe discuss the electron density oscillations in an interacting onedimensional electron system with an impurity [1]. Under appropriate\nconditions the wave vector is given by di\ufb00erent values kF = kL\/R\non left\/right side of the scatterer, leading to a Landauer dipole formation. While in the non-interacting system the Friedel oscillations\npossess only one periodicity related to the local kL on the left side,\nthe interplay of the interactions and non-equilibrium e\ufb00ects generates\nan additional peak in the spectrum of density oscillations at kR . The\nposition and shape of this spectral feature, which in coordinate space\nis observable as a beating pattern in the Friedel oscillations, reveals\nmany important details about the nature of interactions. We believe\nthat it has a potential to become an investigation tool in condensed\nmatter physics.\n[1] D.F.Urban and A.Komnik, Phys. Rev. Lett. 100, 146602 (2008)\nTT 2.2\nMon 10:30\nHSZ 301\nScanning probe measurements and electromigration of metallic nanostructures under ultra-high vacuum conditions \u2014\n\u00a8\n\u00a8\n\u2022Dominik Stoffler1 , Shawn Fostner2 , Hilbert v. Lohneysen1,3 ,\n\u00a8\nPeter Grutter2 , and Regina Hoffmann1 \u2014 1 Physikalisches Institut and DFG Center for Functional Nanostructures (CFN), Universit\u00a8t\nKarlsruhe, D-76128 Karlsruhe, Germany \u2014 2 Physics Department,\nKarlsruhe, Institut f\u00a8r Festk\u00a8rperphysik, D-76021 Karlsruhe, Germany\nQuantum e\ufb00ects play an important role in metal contacts of nanometer size. We use e-beam litho-graphy as well as shadow evaporation\nthrough a stencil mask to fabricate nanobridges made of gold and\nplatinum. The bridges are subject to feedback-controlled electromigration in ultra-high vacuum (UHV). While investigating the e-beam\nfabricated platinum structures with the scanning tunneling microscope\n(STM) in UHV we discovered dense topographically higher features in\nregions of anteceding STM scans, suggesting deposition of additional\nmaterial, possibly carbon, of up to 10 nm thickness. We imaged these\nregions with STM as well as with scanning electron microscopy (SEM).\nTo avoid such a deposition on the metallic bridges we used atomic\nforce microscopy to investigate the electromigration in UHV. The gold\nwires show no fundamental di\ufb00erence to electromigration under ambient conditions. Platinum wires need a higher voltage to start the\nelectromigraton process compared to gold wires. We have obtained\nimages with 3 nm resolution and have observed conductance plateaus\nrelated to the atomic structure of the resulting gold nanocontacts.\nTT 2.3\nMon 10:45\nHSZ 301\nNon-equilibrium transport through coupled quantum dot\u2013\nmetallic island systems \u2014 \u2022Marco G. Pala1 , Michele\n\u00a8\n\u00a8\nGovernale2 , and Jurgen Konig2 \u2014 1 IMEP-LAHC, INP MINATEC,\nCentre National de la Recherche Scienti\ufb01que, 38016 Grenoble, France\nGermany\nWe study transport through a system composed of a single-level quantum dot tunnel-coupled to a metallic island. Such a system is of interest since it can be used to model transport trough a large island in\nseries with charge trap centers [1]. A real-time diagrammatic technique\n[2,3], capable of accounting for non-equilibrium, Coulomb interaction\nand high-order tunneling processes, is employed to investigate transport in the resonant tunneling regime under the in\ufb02uence of a \ufb01nite\ninteraction strength between the dot and the island.\n[1] M. Hofheinz et al., Eur. Phys. J. B 54, 299 (2006).\n[2] J. K\u00a8nig, H. Schoeller, and G. Sch\u00a8n, Phys. Rev. Lett. 76, 1715\n(1996).\n[3] H. Schoeller and G. Sch\u00a8n, Phys. Rev. B 50, 18436 (1994).\nElectron counting experiments attempt to provide a current of a known\nnumber of electrons per unit time. We propose architectures utilizing\na few readily available electron-pumps or turnstiles with the typical\nerror rates of 1 part per 104 with common sensitive electrometers to\nachieve the desirable accuracy of 1 part in 108 . This is achieved not\nby counting all transferred electrons but by counting only the errors of\nindividual devices; these are less frequent and therefore readily recognized and accounted for. We thereby ease the route towards quantum\nbased standards for current and capacitance.\nTT 2.5\nMon 11:00\nHSZ 301\nError Acconting in Electron Counting Experiments \u2014\nHSZ 301\nWe show [1] that harmonic frequency mixing in quantum dots coupled to two leads under the in\ufb02uence of time-dependent voltages of\ndi\ufb00erent frequency is dominated by interaction e\ufb00ects. This o\ufb00ers a\nunique and direct spectroscopic tool to access correlations, and holds\npromise for e\ufb03cient frequency mixing in nano-devices. Explicit results are provided for an Anderson dot and for a molecular level with\nphonon-mediated interactions.\n[1] M. Thorwart, R. Egger, and A.O. Gogolin, Phys. Rev. Lett.\n101, 036806 (2008)\n15 min. break\nTT 2.6\nMon 11:45\nHSZ 301\nNonequilibrium Transport in the Interacting Resonant Level\nModel \u2014 \u2022Peter Schmitteckert \u2014 Institut f\u00a8r Nanotechnologie,\nThe Density Matrix Renormalization Group (DMRG) method is now\na well established method to study interacting, low-dimensional quantum systems. In this talk I review the linear conductance calculations\nof the Kubo approach and the \ufb01nite bias conductance calculations from\nreal time simulations within DMRG. I will then discuss the \ufb01nite bias\nconductance of the interacting resonant level model and compare to\nanalytical calculations based on integrability in the continuum limit.\nThe two approaches are in excellent agreement, and uncover among\nother things a power law decay of the current at large voltages when\nU > 0.\n[1] Edouard Boulat, Hubert Saleur, and Peter Schmitteckert, Twofold Advance in the Theoretical Understanding of Far-FromEquilibrium Properties of Interacting Nanostructures, Phys. Rev.\nLett. 101, 140601 (2008).\nTT 2.7\nMon 12:00\nHSZ 301\nApplication of the weak-coupling CTQMC method to a\nQuantum Dot coupled to superconducting leads \u2014 \u2022David J.\nAstrophysik, Universit\u00a8t W\u00a8rzburg, D-97074 W\u00a8 rzburg, Germany\nWe apply the weak-coupling continuous time quantum Monte Carlo\n(CTQMC) method to the Anderson-model extended by a BCS term\nto describe a quantum dot coupled to s-wave superconducting leads.\nAs the superconducting gap \u2206 grows, our data shows a phase transition\nfrom the 0- to \u03c0-junction regime of the Josephson current. By examining various spectral functions, we con\ufb01rm the traditional interpretation\nthat the Kondo-e\ufb00ect at small \u2206 corresponds to the 0-junction-regime,\nwhile the formation of a magnetic moment on the quantum dot leads to\nthe \u03c0-phase-shift at large \u2206. At constant \u2206, the double occupancy as\na function of U shows a jump, thereby signaling a \ufb01rst order transition\nbetween the singlet and local moment doublet regimes.\nWithin DMFT, this impurity problem provides a link to the periodic\nAnderson model (PAM) with superconducting conduction electrons.\nThe signature of this \ufb01rst order transition in the impurity model in\nthe PAM will be discussed.\nTT 2.8\nTT 2.4\nMon 11:15\nInteraction-induced harmonic frequency mixing in quantum\ndots \u2014 \u2022Michael Thorwart1 , Reinhold Egger2 , and Alexander\nO. Gogolin3 \u2014 1 FRIAS, Universit\u00a8t Freiburg \u2014 2 Universit\u00a8t D\u00a8 ssela\na u\ndorf \u2014 3 Imperial College London\nMon 12:15\nHSZ 301\nWeak localiza","kit-publication-id":"230075150"}]