Bulletin of the American Physical Society
2019 Annual Meeting of the APS Far West Section
Volume 64, Number 17
Friday–Saturday, November 1–2, 2019; Stanford, California
Session E02: Condensed Matter and Applied Physics |
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Chair: Michael R. Peterson, California State University, Long Beach Room: Science Teaching and Learning Center STLC 114 |
Saturday, November 2, 2019 8:30AM - 8:42AM |
E02.00001: Evaporation Induced Rayleigh-Taylor Instability in Aqueous Polymer Solutions Endre Joachim Mossige, Vinny Chandran Suja, Gerald Fuller Understanding the mechanics of detrimental convective instabilities in drying polymer solutions is crucial in many applications such as the production of film coatings. It is well known that solvent evaporation in polymer solutions can lead to Rayleigh-B{\'e}nard or Marangoni-type instabilities. Here we demonstrate another mechanism, namely that evaporation can cause the interface to display Rayleigh-Taylor instabilities due to the build-up of a dense layer at the air-liquid interface. We study experimentally the onset time ($t_p$) of the instability as a function of the initial polymer concentration ($c_0$) and molecular weight. In dilute solutions, $t_p$ shows two limiting behaviors. For high diffusivity polymers (low molecular weight), the pluming time scales as $c_0^{-2/3}$, while in the absence of diffusion, the pluming time scales as $c_0^{-1}$. Above a critical concentration, $\hat{c}$, viscosity delays the growth of the instability, resulting in $t_p$ scaling as $(\nu/c_0)^{2/3}$. These scaling results are not restricted to polymer solutions or evaporation induced instabilities, but are transferable to other binary systems undergoing gravity driven instabilities. [Preview Abstract] |
Saturday, November 2, 2019 8:42AM - 8:54AM |
E02.00002: Non-equilibrium transport and enhanced diffusion near biological active carpets Arnold JTM Mathijssen, Francisca Guzman-Lastra, Manu Prakash, Hartmut Loewen Biological activity is highly concentrated on surfaces, from molecular motors and ciliary arrays to sessile suspension feeders and biofilms – together they form the class of `active carpets'. While the physics of active suspensions has raised considerable interest, it remains unclear how energy and momentum injection from active surfaces can drive living systems out of equilibrium. Here we demonstrate that active carpets generate coherent flows towards the substrate, which provides an efficient pathway for replenishing nutrients that feed back into activity. A full theory is developed in terms of gradients in the active matter density and velocity, and applied to bacterial turbulence, topological defects and clustering. Active carpets can also enhance diffusion, which we describe by generalising Fick's laws for this non-equilibrium living system. Our findings show that diversity in carpet architecture is essential to maintain biofunctionality. [Preview Abstract] |
Saturday, November 2, 2019 8:54AM - 9:06AM |
E02.00003: Investigation of Particle-Hole Symmetry in the Fractional Quantum Hall Effect at the Lowest Landau Level Using Realistic Hamiltonians Eduardo Palacios, Michael Peterson Electrons confined to two-dimensions experience the fractional quantum Hall effect (FQHE) at low electron densities, high magnetic fields, and low temperatures. FQHE states are topologically ordered phases characterized by the fractional filling factor $\nu $ which is the electron number divided by the Landau level (LL) degeneracy. Alternatively, under particle-hole conjugation one can consider system in terms of holes (the absence of an electron). The total number of holes in a fractionally filled LL is simply the LL degeneracy minus the number of electrons. Hence, the fractional filling factor of holes is $\nu_{\mathrm{h}}=$ 1 -$\nu $. Naively, if the system maintains particle-hole symmetry, then if the FQHE occurs at filling factor $\nu $ it will also occur at filling factor 1-$\nu $ with all the same properties. However, realistic effects such as finite magnetic fields, disorder, etc. can break particle-hole symmetry at the level of the Hamiltonian. We study the nature of particle-hole symmetry on the FQHE in the lowest Landau level under realistic conditions numerically using exact diagonalization. [Preview Abstract] |
Saturday, November 2, 2019 9:06AM - 9:18AM |
E02.00004: Intertwined Orders in the Emery Model for the Cuprates Ettore Vitali, Adam Chiciak, Hao Shi, Shiwei Zhang Although superconductivity in the Cuprates was observed for the first time more than thirty years ago, a satisfactory theory of the phenomenon is still missing: unraveling the physical mechanism underlying the appearance of a superconducting phase remains one of the biggest challenges in condensed matter physics. Due to the unprecedented increase in the computational power that we witnessed in the last few years, we are now in a unique position to make significant advances: accurate algorithms are now able to accurately study equilibrium states of model hamiltonians, even when the correlations are strong, as it is the case for the Cuprates. We will present mean field and Quantum Monte Carlo results about magnetic order, change order, nematic order and localization in the ground state of the Emery model, a minimal model for the Cuprates. [Preview Abstract] |
Saturday, November 2, 2019 9:18AM - 9:30AM |
E02.00005: Efficient Unitary Method for Simulation of Driven Quantum Systems Spenser Talkington, HongWen Jiang Density matrices evolved according the von Neumann equation are commonly used to simulate the dynamics of driven quantum systems. However, computational methods using density matrices are often too slow to explore the large parameter spaces of solid state quantum systems. We developed a unitary computation method to quickly perform simulations for closed quantum systems, where dissipation to the environment can be ignored. We applied the method to semiconductor quantum dot qubit systems with time-dependent driving, and predicted the dynamic evolutions. As an example, we implement our unitary method for a realistic four-state system [Z. Shi, et al., Nat. Commun. 5, 3020 (2014)], and find that it is two orders of magnitude faster than the corresponding density matrix method implemented in the popular quantum simulation software QuTiP. In addition, we performed a parameter space exploration. [Preview Abstract] |
Saturday, November 2, 2019 9:30AM - 9:42AM |
E02.00006: Cargo diffusion shortens single-kinesin runs John Wilson, David Quint, Ajay Gopinathan, Jing Xu Molecular motors such as kinesin-1 drive active, long-range transport of cargos along microtubules in cells. Thermal diffusion of the cargo can impose a randomly directed, fluctuating mechanical load on the motor carrying the cargo. Recent experiments highlighted a strong asymmetry in the sensitivity of single-kinesin run length to load direction, raising the intriguing possibility that cargo diffusion may non-trivially influence kinesin. To test this possibility, here we employed Monte Carlo-based simulations to evaluate the transport of cargo by a single kinesin. Our simulations included physiologically relevant viscous drag on the cargo and interrogated a large parameter space of cytoplasmic viscosities, cargo sizes, and motor velocities that captures their respective ranges in living cells. We found that cargo diffusion significantly shortens single-kinesin runs. This diffusion-based shortening is countered by viscous drag, leading to an unexpected, non-monotonic variation in run length as viscous drag increases. To our knowledge, this is the first identification of a significant effect of cargo diffusion on motor-based transport. Our study highlights the importance of cargo diffusion and load-detachment kinetics on single-motor function. [Preview Abstract] |
Saturday, November 2, 2019 9:42AM - 9:54AM |
E02.00007: Calculations of the radiation dose in optically stimulated luminescence dosimeters irradiated by a microbeam. Sarah Kroeker, Mihai Gherase Lead (Pb) is a well-known toxic element accumulating in the human bone following years or decades of exposure. In vivo bone Pb concentration measurements are achieved using the K-shell x-ray fluorescence (KXRF) method based on the excitation of 88.0 keV gamma rays from a Cd-109 source. Due to lower binding energies of Pb L-shell electrons, the alternative L-shell XRF (LXRF) could be more practical by using the excitation of a portable x-ray tube. However, despite past research efforts, lower Pb detection limits and an inaccurate calibration method hindered LXRF from becoming a viable in vivo method. Using a microbeam XRF system and soft tissue and Pb-doped bone phantoms, we developed an optimal grazing-incidence position method to enhance Pb detection by mitigating the x-ray scatter and a new calibration method based on the Sr K$\beta $/K$\alpha $ ratio measurements. LXRF also requires a low radiation dose to the soft tissue per bone Pb measurement. We are currently measuring radiation doses using commercial optically-stimulated luminescence dosimeters. To aid the interpretation of the final results, the absorbed dose to OSLDs was calculated to be in the 6.6 mGy to 12.9 mGy range corresponding to x-ray beam attenuated by soft tissue of thickness varying from 10 mm down to 0 mm. [Preview Abstract] |
Saturday, November 2, 2019 9:54AM - 10:06AM |
E02.00008: Multiple I/O variation of transmission through a double-ring nanoscale structure Eric Hedin, Joel Stock A tight-binding model of the Schrodinger equation is used to analyze the electron transmission properties of a nano-scale double-ring structure (with six embedded quantum dots per ring). The structure's transmission is studied with inputs at 3 different sites and outputs at 4 different sites. A high degree of variation in the system performance is observed, based on the specific choice of input/output positions. This system can also provide a model for a molecular naphthalene structure. A primary emphasis of the analysis of this system is the dependence of transmission to a particular output site as a function of coupling to other output sites. Interference between conduction paths produces transmission variation with both negative and positive dependence on output coupling strengths to other output leads. Magnetic flux through the ring structure also plays a role in the transmission properties through the Aharonov-Bohm effect. [Preview Abstract] |
Saturday, November 2, 2019 10:06AM - 10:18AM |
E02.00009: The Energy SuperGrid (2002): Prelude to the Green New Deal? Paul Grant At the turn of the 20th century, in collaboration with Chauncey Starr,$^{\mathrm{1}}$ recognized founder of the nuclear power industry worldwide, the author proposed the concept of The Energy SuperGrid,$^{\mathrm{2}}$ a symbiosis of nuclear/hydrogen/superconductivity/solar/biomass technologies to supply carbon-free, non-intrusive green energy to support the lives of all inhabitants of our planet throughout the upcoming 21st century and beyond.$^{\mathrm{3}}$ We suggest the Energy SuperGrid concept contains the central elements of the ``Green New Deal'' as proposed as a central issue to be confronted in the upcoming 2020 US election process. We will focus on several physics issues we believe necessary to address for the successful implementation of the ``GND,'' especially those involving nuclear fission and high temperature superconductivity. \begin{enumerate} \item http://w2agz.com/Chauncey{\%}20Starr.htm . \item http://w2agz.com/PMG{\%}20SuperGrid{\%}20Home.htm . \item P. M. Grant, et al, A Power Grid for the Hydrogen Economy, Scientific American, July 2006, p. 78. \end{enumerate} [Preview Abstract] |
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