Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session L44: Onsager, Kadanoff, Davisson-Germer Prize SessionInvited
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Sponsoring Units: DCMP GSNP Chair: Greg Huber Room: BCEC 210C |
Wednesday, March 6, 2019 11:15AM - 11:51AM |
L44.00001: Lars Onsager Prize Talk: Scaling down the laws of thermodynamics Invited Speaker: Christopher Jarzynski Thermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, it is hard to deny that nanoscale systems also exhibit “thermodynamic-like” behavior – for instance, biomolecular motors convert chemical fuel into mechanical work. To what extent can the laws of thermodynamics be “scaled down” to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will describe some of the recent progress and challenges associated with addressing these questions. |
Wednesday, March 6, 2019 11:51AM - 12:27PM |
L44.00002: Dissertation Award in Statistical and Nonlinear Physics Talk: The emergence of collective modes, ecological collapse and directed percolation at the laminar-turbulent transition Invited Speaker: Hong-Yan Shih How a laminar flow becomes turbulence has been an unsolved problem for 130 years and is important in various industrial applications. Only since a decade ago, precise measurements in pipe flow experiments showed non-trivial spatio-temporal complexity at the onset of turbulence where lifetime and splitting time of metastable turbulence do not diverge asymptotically as would have been expected in a sharp transition. Based on numerical evidence in the Navier-Stokes equations, we discovered the surprising fact that the fluid behavior at the transition is governed by the emergent predator-prey dynamics of the important long-wavelength mode, leading to the mathematical prediction that the laminar-turbulent transition is a non-equilibrium phase transition in the directed percolation universality class. This prediction explains the universal scaling laws in experimental observations, and provides a unified picture of transition to turbulence emerging in systems ranging from turbulent convection to magnetohydrodynamics. |
Wednesday, March 6, 2019 12:27PM - 1:03PM |
L44.00003: Leo P. Kadanoff Prize Talk: Complex flows and topology in active matter Invited Speaker: M Cristina Marchetti Active matter is the named coined to describe collections of interacting self-driven entities that spontaneously organize in active fluids and solids, with nonequilibrium transitions between ordered and disordered states. Examples include subcellular structures, groups of motile organisms, and chemical and mechanical analogues with life-like properties. The distinguishing property of active systems is that they are driven out of equilibrium by a forcing that acts independently on each unit, breaking detailed balance at the micro-scale and resulting in behaviors that challenge our intuition. For instance, active fluids flow with no externally applied forces and active gases do not fill their container. After highlighting some of these behaviors, I will focus in this talk on the self-sustained flows of active nematics where the proliferation of motile topological defects mediates the transition to spatiotemporal chaotic dynamics. I will conclude by identifying some of the challenges that lie ahead. |
Wednesday, March 6, 2019 1:03PM - 1:39PM |
L44.00004: Davisson-Germer Prize in Atomic or Surface Physics Talk: Studies of Two-dimensional Materials using Tunneling Electrons Invited Speaker: Randall Feenstra Over the past decade, much research world-wide has focused on two-dimensional (2D) materials, in which the electrons are localized within a single atomic plane. Obtaining μm-size flakes of 2D material by “exfoliating” (peeling apart) layers using adhesive tape has been a standard practice for decades, but only recently has this method been applied to produce small, microfabricated electronic devices on the flakes (Geim and Novoselov, Nobel Prize 2010). However, for practical electronics of the future, such devices must be produced on grown (deposited), large-area 2D layers, rather than on flakes. In this talk, studies of the structure of grown 2D layers will be described, focusing on heterobilayers of MoS2 on WSe2. The method of scanning tunneling microscopy is used to obtain detailed, atomic-scale views of the structure of the layers. Additionally, through spectroscopic measurements with the tunneling microscope, band gaps of the materials and band offsets between neighboring layers are determined. We find, in particular, the occurrence of localized electron states associated with the moiré pattern that forms when one layer of a 2D material (MoS2) is placed on another layer (WSe2) with different lattice constant. |
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