Bulletin of the American Physical Society
2015 Annual Fall Meeting of the APS Ohio-Region Section
Volume 60, Number 12
Friday–Saturday, October 16–17, 2015; Cleveland, Ohio
Session E3: Condensed Matter and Material Science - Theoretical and Computational |
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Chair: Ulrich Zurcher, Cleveland State University Room: SC311B |
Saturday, October 17, 2015 9:15AM - 9:27AM |
E3.00001: Dynamical Energy Gap Engineering in Graphene via an Oscillating Deformation Dawei Zhai, Nancy Sandler Graphene is a fascinating material with various unusual electronic, mechanical and optical properties. One of its most intriguing aspects is the close relation between the electronic properties and mechanical deformations. Interestingly, the effects of deformations can be understood in terms of pseudo-magnetic fields, whose spatial distribution and intensity could be tuned via elaborate mechanical engineering. Previous results have shown that electromagnetic fields (lasers) can induce dynamical gaps in graphene’s energy bands, transforming graphene from a semimetal to a semiconductor. However, the laser frequencies required to achieve these effects are in the THz regime, which imposes strong limitations for practical purposes. The aim of our study is to investigate whether dynamical energy gaps can be achieved with pseudo-electromagnetic fields via oscillating mechanical deformations. We show the existence of a dynamical gap in the energy band structure whose energy position is determined by the frequency of the oscillation, while its magnitude can be tuned by the geometry of the deformation. Because graphene flakes are relatively easier to deform, this dynamical-mechanical manipulation strategy appears as a promising venue to engineer electronic properties of graphene devices. [Preview Abstract] |
Saturday, October 17, 2015 9:27AM - 9:39AM |
E3.00002: Nernst's theorem and compressibilities James McNabb, Imtiaz Tanveer, Shigeji Fujita, Salvador Godoy The unattainability of reducing temperature to the absolute zero is shown by using Carnot's theorem. Hence, the unattainability is distinct from Planck--Fermi's statement of Nernst's theorem : the entropy vanishes at zero K. The adiabatic and the isothermal compressibilities approach each other at 0 K. [Preview Abstract] |
Saturday, October 17, 2015 9:39AM - 9:51AM |
E3.00003: Effects of confinement on the all-or-none polymer folding transition Mark Taylor A flexible homopolymer chain with sufficiently short-range interactions undergoes a discontinuous transition from an expanded coil to a compact crystallite analogous to the all-or-none folding transition exhibited by fast-folding proteins. One anticipates that geometric confinement will reduce the entropy of the unfolded chain, thereby stabilizing the folded state and shifting the transition to higher temperature. In this work we study a flexible square-well N-mer chain (monomer diameter d) located between two hard walls forming a slit-like pore (width W) with the chain end-tethered to one wall. We carry out Monte simulations with Wang-Landau sampling to construct the single-chain density of states and use both microcanonical and canonical analyses to characterize phase transitions. When the slit width is similar to the size of the folded chain we observe a modest stabilization effect. Further reduction of the slit width geometrically prohibits the chain from folding into the free-chain ground state. However, a discontinuous all-or-none folding transition still occurs to a flattened crystallite that spans the pore. All-or-none folding persists even to the limit of a very narrow pore (W=d) where the ground-state structure is a quasi-two-dimensional crystal. [Preview Abstract] |
Saturday, October 17, 2015 9:51AM - 10:03AM |
E3.00004: Drude Infiltration: Hastening the Study of Percolation in Porous Materials Donald Priour In some permeable media, transport of fluid or charge occurs through well defined channels. However, in the case of porous materials made up of randomly placed grains (e.g. spheres or polyhedrons), the connectivity of intersecting voids allowing transport on a macroscopic scale is difficult to assess a priori. While techniques such as the Hoshen-Kopelman algorithm are effective in cases where the connectivity scheme is clear, a calculation in which virtual tracer particles bounce from one impenetrable barrier particle to the next (e.g. via specular reflection) permits the exploration of voids in a rigorous fashion to determine whether the system is permeable at a macroscopic level. We discuss a scheme in which a unidirectional infiltration of a porous material is set up by using charged virtual tracer particles subject to a uniform electric field, a realization of the Drude model for charge transport which is adopted in this work to hasten the determination as to whether the system percolates. Preliminary results obtained for percolation through voids among randomly placed penetrating spheres are discussed, and we examine generalizations of unidirectional infiltration calculations to porous materials comprised of non-spherical (e.g. tetrahedral, cubic, or octohedral) grains. [Preview Abstract] |
Saturday, October 17, 2015 10:03AM - 10:15AM |
E3.00005: Non-linear optics of a strongly coupled multiple-cavity polariton Michael Crescimanno Experiments at CWRU have developed cavity organic polaritons that display record-breaking vacuum Rabi splittings of more than an eV (for an optical transition). These strongly coupled polariton systems open an exciting new regime for exploring non-linear optical effects, and we describe a quantum optical model and its experimental consequences for a single and double cavity system currently being studied in the laboratory. Strongly coupled photon-matter systems such as these may be the foundation for technologies including low-power optical switching and computing. [Preview Abstract] |
Saturday, October 17, 2015 10:15AM - 10:27AM |
E3.00006: MagnetoOptic Effects in Ferrofluids Corneliu Rablau, Prem Vaishnava, Jonathan Zeiders, Ronald Tacket, Ronald Kumon Ferrofluids are stable colloidal suspensions of superparamagnetic nanoparticles in a carrier liquid. The ordering and phase transitions of these polarizable media under the effect of an externally applied magnetic field are accompanied by a number of magneto-optic effects such as the Faraday Effect, dichroism and birefringence. However, the investigation of such effects is complicated by the time-dependent behavior of light propagation and scattering through the ferrofluid at the OFF-ON and ON-OFF transients of the magnetic field. In this presentation we report studies of these transients in a number of ferrofluid systems and discuss the correlation between the light-scattering signature pattern and the ordering of nanoparticles in the ferrofluid. In particular we address the origin of a circular pattern produced by light scattered through a thin layers of ferrofluid and contrast it with the patterns produced by longer light paths through the ferrofluid. [Preview Abstract] |
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