Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session Y50: Fluctuation-Induced Forces |
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Sponsoring Units: DAMOP Chair: Jeremy Munday, University of Maryland Room: Hilton Baltimore Holiday Ballroom 1 |
Friday, March 18, 2016 11:15AM - 11:27AM |
Y50.00001: Nanoscale Radiative Heat Transfer between Graphene Ribbon Arrays Zhuomin Zhang, Xianglei Liu Near-field radiative heat transfer between two graphene sheets can exceed that between blackbodies due to surface plasmons excited by the graphene sheet. This study shows that, by patterning a single layer of graphene sheet into ribbons, a giant enhancement of the near-field radiative heat flux, by more than one order of magnitude higher than that between two graphene sheets, can be achieved. The mechanism lies in that when the graphene sheet is patterned into an array of ribbons, the closed circular dispersion of graphene plasmons is opened to become hyperbolic, leading to broadband singularities of density of states. Extremely high-k evanescent waves can now couple with hyperbolic graphene plasmons. Exact numerical simulations are used by combining the scattering theory and rigorous coupled-wave analysis. Furthermore, effective medium calculations are used to support the arguments and provide clear physical insights. The findings from this study may open promising pathways for highly efficient thermal management, energy harvesting, and subwavelength thermal imaging. [Preview Abstract] |
Friday, March 18, 2016 11:27AM - 11:39AM |
Y50.00002: Failure of local FDT in fluctuation-induced interactions. Diego Dalvit, Francesco Intravaia, Ryan Behunin, Carsten Henkel, Kurt Busch In the study of non-equilibrium fluctuation-induced interactions (e.g., quantum friction, near-field heat transfer, and non-equilibrium Casimir forces) the local fluctuation-dissipation theorem (FDT) is widely used without much justification. Here, we report the failure of the local FDT in a specific example of quantum friction of an atom moving at constant velocity above a surface. A generalized non-equilibrium FDT is derived, which contains a contribution akin to the local FDT and an additional one corresponding to a velocity-dependent current term. We show that in the low-velocity limit the frictional force arising from the current term is of the same order of magnitude as that predicted by the local FDT, which underestimates the total force by almost 50 percent. [Preview Abstract] |
Friday, March 18, 2016 11:39AM - 11:51AM |
Y50.00003: Fluctuation-Induced Interactions in external magnetic fields: Casimir force and Radiative Heat Transfer Raul Esquivel-Sirvent Thermally induced electromagnetic fields give rise to the Casimir force and the near field heat transfer between two bodies separated by a gap. These phenomena are described by Rytov´s theory of fluctuating electromagnetic fields and both the Casimir force and the near field heat transfer depend on the local dielectric function of the bodies. In this work we present a theoretical calculation on the modulation of fluctuation-induced interactions in the presence of an external magnetic field. The system consists of two parallel plates separated by a gap $d$. Each plate is isotropic and has a local dielectric function. Applying an external magnetic field parallel to the plates, in the so called Voigt configuration, the plates become anisotropic. In particular, we consider plates of InSb. For the Casimir force the two plates are kept at the same temperature and the external field reduces the magnitude of the force. Similarly if the two plates are kept at different temperature the near field radiative heat transfer is modulated by the magnitude of the external magnetic field. The results are extended to semiconducting quantum wells. In both cases, the excitation of magnetoplasmons provides an explanation for the observed effect. [Preview Abstract] |
Friday, March 18, 2016 11:51AM - 12:03PM |
Y50.00004: Short distance expansion for fluctuation induced interactions Thorsten Emig, Giuseppe Bimonte Fluctuation induced interactions become most prominent in close to proximity to surfaces. Examples include van der Waals and Casimir forces, heat transfer, and spectral shifts for atoms and molecules. In many situations, the surfaces are curved or structured which makes the computation of the interaction in general complicated. Here we present a versatile and powerful approach to this problem which is based on a derivative expansion. It applies to distances much smaller than the radii of surface curvature. Explicit results include orientational effects for anisotropic particles, thermal effects, and spectral modifications. [Preview Abstract] |
Friday, March 18, 2016 12:03PM - 12:15PM |
Y50.00005: Unified boundary conditions and Casimir forces for fields with arbitrary spin Robert Bennett, Adam Stokes The electromagnetic Casimir effect is well-known and has been extensively studied for the last half-century. This attractive force between parallel plates arises from the imposition of boundary conditions upon the fluctuating spin-1 photon field, so a natural further question is wether fields of different spin can cause similar forces when confined in the same way. However, so far it has not been clear what the appropriate boundary conditions for physically-confined spinor fields may be. Here we present work that generalises the physically well-motivated electromagnetic boundary conditions to fields of arbitrary spin, thus arriving at physically reasonable boundary conditions\footnote{A. Stokes and R. Bennett, New J. Phys. 17 073012 (2015)} and Casimir forces\footnote{A. Stokes and R. Bennett, Ann. Phys NY 360 246 (2015)} for a selection of interesting fields. For example, the so-called `bag model' boundary conditions from nuclear physics emerge from our generalised boundary condition as a special case, as do the linearised gravity boundary conditions suggested in a remarkable recent proposal\footnote{James Q. Quach, Phys. Rev. Lett. 114 081104 (2015)} concerning possible measurement of gravitonic Casimir forces. [Preview Abstract] |
Friday, March 18, 2016 12:15PM - 12:27PM |
Y50.00006: Measurement and control of electrostatic patch potentials Joseph L Garrett, Jeremy N Munday Electrostatic patch potentials hinder many precision measurements, particularly measurements of the Casimir force. Despite the improved force sensitivity achieved over the last decade, only recently have attempts been made to measure and quantify the effects of patch potentials. Here we present an analysis of patch potentials measured by Kelvin probe force microscopy (KPFM) and discuss methods to control these potentials (e.g. humidity, material choice, etc). [Preview Abstract] |
Friday, March 18, 2016 12:27PM - 12:39PM |
Y50.00007: An experimental apparatus for Casimir torque measurements David A.T. Somers, Jeremy N. Munday We have developed an experiment to measure the Casimir torque. In our experiment, a solid birefringent crystal causes a nematic liquid crystal director to rotate such that the extraordinary axes are aligned. A transparent and isotropic dielectric spacer layer is used to separate the two birefringent materials and an all-optical technique is used for detection. In this talk, we report on the progress of this experiment. [Preview Abstract] |
Friday, March 18, 2016 12:39PM - 12:51PM |
Y50.00008: Parameterization of lattice spacings for lipid multilayers in ionic solutions Horia Petrache, Merrell Johnson, Daniel Harries, Soenke Seifert Lipids, which are molecules found in biological cells, form highly regular layered structures called multilamellar lipid vesicles (MLVs). The repeat lattice spacings of MLVs depend on van der Waals and electrostatic forces between neighboring membranes and are sensitive to the presence of salt. For example, addition of salt ions such as sodium and potassium makes the MLVs swell, primarily due to changes in electrical polarizabilities. However, a more complicated behavior is found in some ionic solutions such as those containing lithium ions. Using x-ray scattering, we show experimentally how the interactions between membranes depend on the type of monovalent ions and construct parameterizations of MLVs swelling curves that can help analyze van der Waals interactions. [Preview Abstract] |
Friday, March 18, 2016 12:51PM - 1:03PM |
Y50.00009: ABSTRACT WITHDRAWN |
Friday, March 18, 2016 1:03PM - 1:15PM |
Y50.00010: ABSTRACT WITHDRAWN |
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