Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session Y33: Nanowires and Quantum Dots |
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Sponsoring Units: DCMP Chair: Milind Kunchur, University of South Carolina Room: 403 |
Friday, March 20, 2009 8:00AM - 8:12AM |
Y33.00001: Digital Wires Benny Brown, Alfred Hubler We study hardware implementations of cellular automata as reliable, adjustable, and secure commication lines. We discuss energy efficient digital wires on a nano-scale, all-optical digital wires, and digital wires as power lines and present performance data of a prototype digital wire, a six cells wide and ten cells long Boolean network. We show that digital wires have the following advantages: (i) Fixed pulse shape (pulses have a rectangular shape with a constant height and a constant width and produce no echos); (ii) Robust against electric smog. Digital wires based on semiconductor technology are effectively inert against electro-magnetic radiation, except for low-frequency radiation (heat) and high frequency radiation (X-rays). Digital wires based on plasma technology have in addition a very high tolerance for heat and X-rays. In digital wire the pulse speed can be rapidly adjusted. Signals on digital wires can be encrypted. Some digital wires can be used as general purpose computers. The data and the code are the input of the wire. Then both travel along the wire and `collide'. The collision is the computation. The result travels to the end of the wire, for further processing, as parallel input by a CPU, an actuator, or another digital wire. [Preview Abstract] |
Friday, March 20, 2009 8:12AM - 8:24AM |
Y33.00002: ABSTRACT WITHDRAWN |
Friday, March 20, 2009 8:24AM - 8:36AM |
Y33.00003: Renormalization of the dephasing by zero point fluctuations Swarnali Bandopadhyay, Doron Cohen One of the most fundamental properties of an quantum particle is to maintain its phase-coherence. When an quantum particle is coupled to a fluctuating environment its wave-function gets phase-randomised. During the last decade a controversy has emerged in the mesoscopic literature regarding the role of zero-point-fuctuations (ZPF) in low temperature dephasing. We propose an exactly solvable model for dephasing due to short range scattering with environmental modes in dephasing at low temperature. Unlike the Caldeira-Leggett model where the interaction is with an homogeneous fluctuating field of force, here we consider the environment consisting of infinitely many localized fluctuating modes with (say) Ohmic spectral function and the interaction is local as in ``s-scattering". We find that in low temperature ZPF can enhance the inelastic cross-section. Our study shows [Phys. Rev. B {\bf 77}, 155438 (2008)] we need finite temperature to see the effect. Thus indirectly ZPF might contribute to the dephasing at low temperature. [Preview Abstract] |
Friday, March 20, 2009 8:36AM - 8:48AM |
Y33.00004: Helical [110] gold nanowires make longer linear atomic chains Edgard Amorim, Edison da Silva Experiments performed on nanowires (NWs) synthesized by electron beam irradiation technique have shown that gold NWs formed along the [110] direction become helical when the NWs are sufficiently thin [1]. Moreover, helical and other non-crystalline structures have been theoretically predicted to other few metals [2]. Our study using tight-binding molecular dynamics show that gold NWs formed along the [110] direction reconstruct upon stress to form helical NWs. We discuss this formation and our results seem to indicate that an intrinsic mechanism is responsible for the formation of the helical structure. These helical NWs evolve on stretching to form linear atomic chains (LACs) and because they do not form symmetrical tips, these NWs produce longer LACs than other NWs. We use \textit{ab initio} calculations to study the NW obtained from the tigth-binding simulations at stages close to rupture and compare LAC distances obtained with both methods. Furthermore, we investigate the electronic structure of the NW close to rupture [3]. [1] Y. Kondo, and K. Takayanagi, Science \textbf{289}, 606 (2000). [2] O. Gulseren, F. Ercolessi and E. Tosatti, Phys. Rev. Lett. \textbf{80}, 3775 (1998). [3] E.P.M. Amorim and E.Z. da Silva, Phys. Rev. Lett. \textbf{101}, 125502 (2008). [Preview Abstract] |
Friday, March 20, 2009 8:48AM - 9:00AM |
Y33.00005: Hall effect detection of time-reversal symmetry breaking under AC driving Alexei Chepelianskii, Sophie Gueron, Frederic Pierre, Antonella Cavanna, Bernard Etienne, Helene Bouchiat In a four terminal sample microscopic time-reversibility leads to symmetry relations between resistance measurements where the role of current and voltage leads are exchanged. These reciprocity relations are a manifestation of general Onsager-Casimir symmetries in equilibrium systems. We investigate experimentally the validity of time reversal symmetry in a $GaAs/Ga_{1-x}Al_xAs$ Hall bar irradiated by an external AC field at zero magnetic fields. For inhomogeneous AC fields we find strong deviations from reciprocity relations and show that their origin can be understood from the the billiard model of a Hall junction. Under homogeneous irradiation the symmetry is more robust indicating that time-reversal symmetry is preserved. [Preview Abstract] |
Friday, March 20, 2009 9:00AM - 9:12AM |
Y33.00006: On time-dependent counting statistics of mesoscopic electron transport Wolfgang Belzig Full counting statistics (FCS) has emerged as a key concept to understand quantum transport in mesoscopic systems like heterostructures, quantum wires, and quantum dots. The knowlegde of the FCS not only enables to predict all measurable zero-frequency quantities accessible via charge detection, but also allows to identify the elementary transport events and the correlations between them. We demonstrate this concept for a standard quantum point contact between normal and/or superconducting leads under dc- and ac-bias. [M. Vanevic, Yu. V. Nazarov, W. Belzig, Phys. Rev. Lett. 99, 076601 (2007)] Finally we address the question, how these concepts can be applied to time-resolved current measurements. [A. Bednorz and W. Belzig, Phys. Rev. Lett. 101, 206803 (2008)] [Preview Abstract] |
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