Bulletin of the American Physical Society
2006 Ohio Section of the APS Spring Meeting
Friday–Saturday, March 31–April 1 2006; Detroit, Michigan
Session S5: Probing Novel Phenomena in Materials & Devices |
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Chair: Gavin Lawes Room: McGregor Center FG |
Saturday, April 1, 2006 8:00AM - 8:12AM |
S5.00001: Transmission and phase behavior of an open Aharonov-Bohm ring with a single quantum dot Eric Hedin, Yong Joe, Arkady Satanin The electron transmission and phase, and the AB-oscillation phase of a 3-terminal Aharonov-Bohm (AB) ring with a quantum dot (QD) embedded in one arm are investigated using a tight-binding model. It is shown that in a three-terminal interferometer, the zero of the Fano resonance in the transmission moves off the real energy axis in relation to the degree of coupling of the QD to a third output terminal. A simple analytical model of the Fano resonance shows naturally how the phase transition across the resonance peak will change from an abrupt jump of $\pi $ to a smooth transition when the Fano zero energy is no longer real, but complex. The Fano zero orbits around the pole as a function of magnetic flux through the ring, and can be returned to the real energy axis at specific values of the flux, as long as the coupling parameter is smaller than a critical value. By tuning the degree of coupling to the third lead, the phase of the AB oscillations can be matched to the intrinsic phase of the QD, providing an experimental method of extracting the phase behavior of the QD. *Supported by the Indiana 21st Century Research and Technology Fund. One of the authors (E. R. H.) is partially supported by a grant from the Center for Energy Research, Education, and Service (CERES), at Ball State University. [Preview Abstract] |
Saturday, April 1, 2006 8:12AM - 8:24AM |
S5.00002: Probing Low Magnetic Fields at the Micron Scale V. Batra |
Saturday, April 1, 2006 8:24AM - 8:36AM |
S5.00003: Diffusion of Trace Alkanes in Polyethylene: Spin-Echo Measurements and Monte-Carlo Simulations E. von Meerwall, H. Lin, W.L. Mattice We have performed pulsed-gradient NMR diffusion (D) measurements on five n-alkanes (24, 28, 36, 44, and 60 carbons) in a polyethylene (PE) host (M = 33 kDa) as function of concentration c (2-10 wt.\%) at 180 deg. C. Monte-Carlo simulations on the second-nearest-neighbor diamond lattice (38, 46, 62, and 78 carbons) at c between 2 and 15 wt.\% in a host of PE (M = 4.5 kDa) explored static and dynamic properties. The bridging method uses beads combining adjacent moieties and incorporates two-bead moves; it permits detailed reconstruction of the chain molecules at any stage. It uses discretized short-range rotational isomeric state and long-range intra- and interchain Lennard-Jones potentials. For both experiment and simulation, trace D was obtained by extrapolating D(c) to c = 0 using the Fujita-Doolittle equation with known chain-end free-volume parameters. A ratio of 330 Monte-Carlo steps per picosecond brings simulation into congruence with experiment; this factor is identical to that required for PE melts. The applicability of the Rouse model is approached only for the largest alkanes, but the M(alkane)-dependence of trace D is seen to be in transition from the Rouse-like 1/M-scaling to a steeper value characteristic of reptation with constraint release. [Preview Abstract] |
Saturday, April 1, 2006 8:36AM - 8:48AM |
S5.00004: Cut Growth Patterns in Double Networks of a Natural Rubber Vulcanizate Crittenden Ohlemacher, Gary Hamed The effect of aging at 90 deg. C and 110 deg. C under nitrogen, with and without applied strain, on black-filled natural rubber, with an inefficient sulfur cure was investigated. Samples aged under strain became ``double networks'' and retained a residual extension ratio. Cut growth behavior of the double networks was complex. The perpendicular specimens (cut parallel to the applied strain during aging), had cracks that either were ``super-blunted'' or exhibited ``forward'' crack splitting. Parallel specimens were weaker than perpendicular and single network ones, and exhibited a critical cut size, for which a small increase in cut size resulted in an abrupt decrease in strength. For cuts smaller than the critical size, crack geometries were ``super-blunting'', while specimens with larger cuts typically showed simple lateral propagation, without longitudinal cracking or crack splitting. There was some evidence that parallel double network specimens had greater ability to strain-crystallize. However, decreased cut growth resistance of these suggests that limited chain extensibility is controlling. [Preview Abstract] |
Saturday, April 1, 2006 8:48AM - 9:00AM |
S5.00005: Spin Polarization Measurements of Co$_{1-x}$ - Pt$_x$ Alloys by Point Contact Andreev Reflection Spectroscopy F.M. Muzummal |
Saturday, April 1, 2006 9:00AM - 9:12AM |
S5.00006: High Resolution Magnetic Field Measurements with Scanning Hall Probe Microscope G. Shamsutdinov |
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