Bulletin of the American Physical Society
2013 Annual Fall Meeting of the APS Ohio-Region Section
Volume 58, Number 9
Friday–Saturday, October 4–5, 2013; Cincinnati, Ohio
Session E1: Condensed Matter A |
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Room: Braunstein Hall 300 |
Saturday, October 5, 2013 8:00AM - 8:12AM |
E1.00001: Quantum Conductance of Graphene Nanoribbons (GNRs) Zhe Kan, Chris Nelson, Mahfuza Khatun We will present results of band structure, density of states (DOS), and the effects of defects on the conductance of graphene nanoribbons (GNRs).~ These nanoribbons can be either metallic or semiconducting depending on their edge structures. These are robust materials with excellent electrical conduction properties and have the potential for device applications. A tight-binding (TB) model has been used for the calculation of electronic band structure, and the Green's function method and the Landauer formula have been implemented for determining the transmission and conductance, respectively.~ We have investigated the effects of vacancy, weak disorder, and the presence of oxygen on conductance.~ The resulting local density of states (LDOS) and conductance bands show that electron transport has interesting behavior in the presence of any disorder.~ In general, the presence of any disorder in the GNRs causes a decrease in conductance.~ In the presence of a vacancy at the edge site, a maximum decrease in conductance has been observed which is due to the presence of quasi-localized states. ~ [Preview Abstract] |
Saturday, October 5, 2013 8:12AM - 8:24AM |
E1.00002: Heat Flux and Thermal Conductivity of Carbon Nanotubes (CNTs) Shaun Wood, Chris Nelson, Mahfuza Khatun We report an analysis of heat flux data and thermal conductivity of Carbon Nanotubes (CNTs). These one dimensional (1-D) honeycomb structures are extremely versatile and robust with high thermal and electrical conductivities. They can exist in metallic or semiconducting forms depending on their structures. Successful implementation of such structures will have tremendous technological impacts. The theoretical investigation is based on equilibrium molecular dynamics (EMD) technique where the autocorrelation heat flux functions and the thermal conductivity have been calculated using the Green-Kubo formalism from linear response theory. Two open source codes are used in this investigation. The CNTs are generated using the Visual Molecular Dynamics (VMD) software and the simulations are performed using the code called Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The code is run on the Beowulf Computing Cluster. Thermal conductivity of CNTs with different lengths and temperatures has been calculated and studied. In addition, the time-dependence characteristics of the heat flux functions have been analyzed, and will be discussed. [Preview Abstract] |
Saturday, October 5, 2013 8:24AM - 8:36AM |
E1.00003: Resonance Structure of Series Coupled Aharonov-Bohm Rings with Embedded Quantum Dots Eric Hedin, Yong Joe Series-coupled nanoscale Aharonov-Bohm (AB) rings with a quantum dot (QD) embedded in each arm have shown potential for generating spin-polarized current in conjunction with the Zeeman effect. In this presentation, an overview of the computational results obtained from analyzing the electron transmission through a multiple ring structure will be given, showing the possibility of obtaining either semiconductive or Ohmic current-voltage characteristics. Spin-polarized current as a function of system parameters is shown. In addition, the AB effect has been shown to modify the transmission band structure of the device. Further, the possibility of producing sharpened AB oscillations in the transmission output of the multiple-ring device is demonstrated. [Preview Abstract] |
Saturday, October 5, 2013 8:36AM - 8:48AM |
E1.00004: A new theoretical approach to calculating the probability of charge transfer between atomic orbitals Dale Igram, Eric Hedin, Yong Joe In the world of physics, the probability of charge transfer is more commonly known as tunneling or transmission coefficient where physical parameters such as barrier height and width, and energy of incident particle are considered. However, an alternative approach based on the overlap of the wave functions of atomic orbitals has been developed. The overlap of wave functions is described by an overlap integral parameter $S$ as a function of $pp\sigma$ and $pp\pi$ interactions. We will reveal that the probability of charge transfer is proportional to the ratio of the overlap integral $S$and $S_{\max} $ for two atomic orbitals. Results for several atomic orbital combinations of guanine and cytosine molecules for a B-DNA molecule are presented and discussed. [Preview Abstract] |
Saturday, October 5, 2013 8:48AM - 9:00AM |
E1.00005: Physics of lattice bosons in the presence of occupation parity coupling Kuei Sun, C.J. Bolech Interacting bosons in lattices can exhibit two extremely different phases at low temperature: Mott insulator and superfluid. The system's phase diagram is well described by the Bose-Hubbard (BH) model, which considers onsite repulsion and nearest-neighbor tunneling of bosons. Here we study the physics of a BH system when an interesting ingredient, a ferromagnetic-like coupling between nearest-neighbor sites' occupation parities, is introduced. Our analysis shows that this parity coupling has non-trivial interplay with the tunneling and onsite interaction, resulting in exotic quantum phases such as pair liquid, pair superfluid, phase separation in uniform systems, or a wedding-cake-structured Mott insulators with the occupation jumping by two in trapped systems. We will discuss the properties of these phases and suggest two experimental realizations in cold atom and condensed matter systems. [Preview Abstract] |
Saturday, October 5, 2013 9:00AM - 9:12AM |
E1.00006: Electron transport in Individual GaAs Nanowire Zhuting Sun, Andrei Kogan, Tim Burgess, Chenupati Jagadish We report electrical transport measurements in M-S-M nanowire structures on individual GaAs nanowires approximately 50 nm in diameter contacted via lithographically patterned Al/Ti metal films at various temperatures. The I-V characteristics of the M-S-M structures are device dependent. The measurement results were compared to a phenomenological model, and an analytically procedure for decoupling the M-S(Schottky) contact from the intrinsic parameters of individual GaAs nanowires, such as mobility and carrier density is proposed. We find the wires behave like bulk material at room temperature with the doping density around $10^{18} cm^{-3}$, and the mobility around 8000 $cm^{2}/(V*s)$.The work is supported by NSF grant DMR-1206784 and DMR-0804199 and University of Cincinnati. [Preview Abstract] |
Saturday, October 5, 2013 9:12AM - 9:24AM |
E1.00007: Plasmonic Circular Dichroism of Chiral Nanoparticle Assemblies Zhiyuan Fan, Hui Zhang, Alexander Govorov Chiral metal nanoparticle (NP) assemblies exhibit plasmonic circular dichroism in the visible spectral region. It was found previously that CD signals can be induced by dipolar interactions between nanoparticles of a chiral NP assembly. In this study, we show that plasmonic CD signals can be enhanced by multipole effects in tightly packed nanoparticle assemblies. We have used discrete dipole approximation (DDA) in the simulation of CD signals of nanoparticle tetramers with different geometries, which include an equilateral tetrahedron, a helical structure and an asymmetric pyramid. Our results show that the strength of CD signals rapidly decreases with the interparticle distance as 1/R$^{9.7}$ for the helices and as 1/R$^{18}$ for the equilateral tetrahedral 4-NP complexes, where R is an interparticle distance. On the other hand, plasmonic CD response can also be enhanced through anisotropy. We will show that orientated NP assemblies generally exhibit stronger CD response than those in colloidal system. This study can be useful in the design of chiral nanoparticle structures for sensing and optical applications. [Preview Abstract] |
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