Bulletin of the American Physical Society
2018 Annual Meeting of the Far West Section
Volume 63, Number 17
Thursday–Saturday, October 18–20, 2018; Cal State Fullerton, Fullerton, California
Session F01: Material Science and Theoretical Condensed Matter Physics |
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Chair: Patricia Sparks, Harvey Mudd College Room: Titan Student Union Hetebrink A-B |
Saturday, October 20, 2018 2:00PM - 2:12PM |
F01.00001: Quantum Dot Nanoshells in Single Droplets of Liquid Cryastal Ibrahim M Abu-Hijleh, Tayebeh Riahinasab, Charles N Melton, Linda S. Hirst A common goal of nanoparticle research is to assemble nanoparticles into useful macroscopic structures. Nanoparticles that are dispersed in nematic liquid crystal exhibit predictable behavior; the nanoparticles assemble in regions of low order (topological defects) of the liquid crystal domain. We can use the isotropic-nematic phase transition of 4-Cyano-4'-pentylbiphenyl (5CB) to drive freely dispersed nanoparticles into intricate structures such as nanoparticle hollow shells, but there is need to have control over the dimensions of the shells. In our experiments we demonstrate that we can form individual shells out of quantum dots inside a single droplet of 5CB. We are able to see that there is a positive correlation between the shell size and thickness to the size of the droplet when we fit the data linearly. From this data we can also suggest that there is a threshold size of liquid crystal droplet at which must be met before a hollow shell will form over a solid cluster of quantum dots. |
Saturday, October 20, 2018 2:12PM - 2:24PM |
F01.00002: Structurally Induced Magnetic Transition in Manganese Phthalocyanine Thin Films Anh Nguyen, Thomas Gredig Manganese phthalocyanine (MnPc) thin films were fabricated on both insulating and metallic substrates at different deposition temperatures ranging from 32^{o}C to 260^{o}C using thermal evaporation. Two crystal structures are found: one set of thin films shows the MnPc (200) 2θ peak between 6.732^{o} and 7.004^{o} corresponding to a lattice constant ranging from 2.280 nm to 2.395 nm. The second set deposited at 230^{o}C and 260^{o}C has a MnPc (001) 2θ peak at 7.12^{o} consistent with MnPc in the β-phase and a lattice constant corresponding to c = 1.306 nm. The structural change is accompanied by changes in the magnetism. The magnetic properties of all MnPc thin films are characterized with the vibrating sample magnetometer. The temperature-dependent static susceptibility shows a large increase at low temperatures for samples deposited in the β-phase, simultaneously the low-temperature magnetic hysteresis loops have a large saturation magnetization for the same set of samples. The net magnetization disappears for the low-temperature sample set. This is characteristic for a magnetic transition with the parameter being the crystalline order of the material. |
Saturday, October 20, 2018 2:24PM - 2:36PM |
F01.00003: A quantum phase transition and novel spin phases in the three-band Hubbard model Ettore Vitali, Adam Chiciak, Hao Shi, Shiwei Zhang The three-band Hubbard model captures several key features of the Copper-Oxide planes in cuprate superconductors, and provides the simplest model beyond the minimal one-band Hubbard model. Combining extended mean-field calculations with cutting-edge correlated methodologies we are performing an extensive study of the model in the relevant regions of the parameter space. We address the nature of the spin and charge order, as well as of pairing correlations, as a function of the interaction strength and the charge transfer energy in the ground state of this model. We find evidence of a quantum phase transition at half-filling and very interesting novel spin states in the underdoped regime. |
Saturday, October 20, 2018 2:36PM - 2:48PM |
F01.00004: Critical Temperature of Superconducting Magnetic Hybrid Systems Renyu Wang, Adam Moke, Andreas Bill We study proximity systems made of coupled thin films with superconducting and magnetic ground states. We analyze how varying parameters of the magnetic component affects the superconducting critical temperature T_{c }of the entire system. Singlet Cooper pairs formed in the superconducting layer permeate into the magnetic material resulting in the generation of triplet pair correlations that may modify T_{c}. The critical temperature is calculated by solving Usadel’s equations using an involved transformation to an eigenvalue problem. The method is a generalization of previous work that enables us to include magnetic inhomogeneities. We apply the method to a trilayer SF_{1}F_{2} where F_{1} and F_{2} have different magnetic properties. Specifically, we study the behavior of T_{c} as a function of the thickness and magnetization twisting angle of F_{1} with respect to F_{2}. |
Saturday, October 20, 2018 2:48PM - 3:00PM |
F01.00005: Periodic Table Mapping of High Temperature Superconductors O'Paul Isikaku-Ironkwe The Periodic Table of Elements (PTE), a systematic database of all known elements, has predictive powers through periodicity of electronegativity, atomic and ionic radii, ionization energy and other parameters. In the search for novel superconductors, the PTE has been a useful guide to researchers. The original basic principles of the PTE was classifying the elements in increasing mass per unit atom. This was eventually extended to include atomic numbering, chemical groups and Periods. We harness the same principles to classify superconductors, treating them as “super-atoms’ and hence “layered elements”. We will show that this classification scheme of high temperature superconductors (HTSCs) into the Periodic Table, produces some interesting predictability and aid in the search for novel HTSCs: in particular, higher transition temperatures exist in lower Periods of the Periodic Table of HTSCs. |
Saturday, October 20, 2018 3:00PM - 3:12PM |
F01.00006: Optimal foraging strategies for territorial competitors Farnaz Golnaraghi, Ajay Gopinathan Many animals such as albatrosses are known to exhibit foraging patterns where the distances they travel in a given direction are drawn from a heavy tailed Levy distribution. Previous studies have shown under sparse resources, solitary foragers perform an optimally efficient search with Levy exponent equal to 2. However, in nature, there also exist situations where multiple foragers interact with each other either cooperatively or competitively. We develop a stochastic agent-based simulation that models foraging with competitive interactions. In our simulations each forager has a territory with a certain size around itself which is not accessible by the others. We show that by increasing the size of the territory, and number of agents, the efficiency of the search decreases, and the optimal Levy exponent shifts toward values larger than 2, indicating that more localized searches are more efficient in the presence of competition. Finally, we show that the variance among the efficiencies of the agents increases with increasing Levy exponent. Thus, by performing more localized searches, foragers might increase mean efficiency, but with the risk of increasing fluctuations in efficiency. |
Saturday, October 20, 2018 3:12PM - 3:24PM |
F01.00007: Levy Walks in Non-Euclidean Spaces Imtiaz A Ali, Ajay Gopinathan, David quint Many animals display characteristic foraging patterns in their behavior when searching for food. Previous studies on foraging have shown that, in many cases, animals follow a Levy flight pattern with a power law distribution of step sizes that might be tuned for optimal search efficiency. While all of biology is constrained to live in Euclidean space, natural search processes may take place in effectively more complex spaces with a network topology such as networks of caves or other ecological niches. Motivated by the recent equivalency that has been shown to exist between complex scale-free networks and hyperbolic space, we consider the question of optimal foraging in the case when searching occurs in a negatively curved space. We study the search process in an appropriate projection of the hyperbolic space and make use of the equivalency to infer connections between optimal Levy walk searching in hyperbolic space and searching on a scale-free network. |
Saturday, October 20, 2018 3:24PM - 3:36PM |
F01.00008: Thermodynamic properties of mesoscopic systems Sreemoyee Mukherjee In last few decades mesoscopic physics has emerged as a prominent area of research and development. It promises to give rise to a new generation of electronic devices that work on quantum principles. Although these devices can revolutionize the electronic industry, have not been achieved yet as it is difficult to control their stability. We have shown that one can use evanescent modes to build stable quantum switches using a multichannel Aharonov-Bohm interferometer, where we proposed a new S matrix. Using A-B interferometer we explained magnetic induction generated by transport current. Quantum tunneling of an electron through a classically forbidden regime has no classical analogue. We analyzed a situation where electronic current under the barrier can be measured using evanescent modes. We showed unlike other proposed quantum devices such currents are not sensitive to changes in material parameters and thus the system can be used to build stable devices that work on magnetic properties. Capacitance of a system is self consistently determined by Coulomb interaction and this is no exception for quantum capacitance. We started from microscopic approach to many body physics and showed the analytical steps and approximations required to arrive at the concept of quantum capacitance. |
Saturday, October 20, 2018 3:36PM - 3:48PM |
F01.00009: Large Deviations in Thermodynamic Computation Cina Aghamohammadi, James P. Crutchfield We propose a framework for the study of large deviations in thermodynamic computation with a long memory. The thermodynamic computation is done by a machine in contact with thermal reservoir known as information engine which manipulates information on the input to tape to information on the output tape by some given stochastic law. Information on the input tape can be highly correlated with a really long memory and as a result, Non-Markovian which makes the problem non-trivial. Here we study large deviations of computation accuracy and also cost of computation. |
Saturday, October 20, 2018 3:48PM - 4:00PM |
F01.00010: Entanglement entropy study for the Half-Filled Extended Hubbard model Jon D Spalding The problem of interacting electrons is the modern frontier of condensed matter physics, in which exotic emergent phases combine with analytical intractability to create an exciting arena for discovery and application of new numerical methods. In this talk, we present new results from the application of quantum information theory to the precise identification of the phase boundaries for Bond-Order-Wave ordering in the 1-D Extended Hubbard model. In particular, we show that for this canonical model of long-range electron interactions, a new, simple scaling method enables the precise extraction of critical points for both 2nd order and BKT universality class quantum phase transitions. This method requires nothing besides the ground-state wavefunction and John Cardy's formula for the entanglement entropy at conformally-invariant critical points. |
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