Bulletin of the American Physical Society
2018 Annual Fall Meeting of the APS Ohio-Region Section
Volume 63, Number 15
Friday–Saturday, September 28–29, 2018; University of Toledo, Toledo, Ohio
Session A02: Condense Matter Physics I |
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Chair: Max Junda, The University of Toledo Room: SU 2584 |
(Author Not Attending)
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A02.00001: Electronic Compressibility and Magnetic Susceptibility in the Repulsive Hubbard Model away from Half-Filling Ian Riley Osborne The Hubbard Model, noteworthy for its simplicity, is observed to possess multiple fascinating quantum phase transitions with rich physics and implications that have yet to be explored thoroughly. We quantitatively examine the response functions, electronic compressibility (κ) and magnetic susceptibility (χ), in the Repulsive Fermi-Hubbard model using Quantum Monte Carlo (QMC) techniques within the parameter space of temperature and interactions away from half filling. The equivalence of these response functions in the t >>U metallic phase is noted; and an analytic relation between κ and χ is derived as a function of density correlators. We analyze the phase diagram of the Fermi-Hubbard Model and suggest a likely, novel non-Fermi Liquid phase, as well as discuss the significance and consequences of such a phase. |
(Author Not Attending)
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A02.00002: Topological Entanglement Entropy in the J1-J2 Quantum Antiferromagnet on a Square Lattice Michael Ferrarelli, David Ronquillo, Nandini Trivedi We employ exact diagonalization to calculate the ground state wave function of the next-nearest neighbor J1-J2 quantum antiferromagnet on a square lattice with 16 sites. Previous reports drawing attention to the magnetically frustrated regime in parameter space, roughly between 0.4 < J2/J1 < 0.6, have reported the presence of a valence bond crystal or gapless spin liquid phase. Using the Kitaev-Preskill Construction, we calculate a finite topological entanglement entropy (TEE) within this frustrated intermediate regime, suggesting the presence of a topologically ordered spin liquid phase. |
Friday, September 28, 2018 2:00PM - 2:15PM |
A02.00003: First-principles study of mechanical and magnetic properties of transition metal (M) nitrides in the cubic M4N structure Vijaya Adhikari, Z. T. Y. Liu, N. J Szymanski, Indiras Khatri, Daniel Gall, Pankaj Sarin, Sanjay V Khare We report results from systematic calculations performed by density functional theory [1] on mechanical properties of twenty-eight 3d, 4d and 5d transition metal (M) nitrides (TMNs) in metal-rich cubic M4N structure as novel candidates for hard coatings materials. Our calculations indicate that all M4N-type metal nitrides except V4N, Nb4N, and Pt4N are mechanically stable. All Group 7 TMNs in the M4N structure are found to have high Vickers hardness values with the highest being 24.3 GPa for Re4N. Our computed lattice constants and magnetic dipole moments for Mn4N and Fe4N are consistent with their measured values. Spin-polarized computations reduce the hardness of some magnetic compounds like Mn4N and Fe4N. The hybridization of metal d and nitrogen 2p orbitals is found to be the key factor in determining mechanical stability and hardness. The database for binary transition metal nitrides in M4N structure offers possibilities for experimental synthesis for the hard-coatings application. [1] V. Adhikari, Z. T. Y. Liu et. al, JPCS, 120, 197, 2018; https://doi.org/10.1016/j.jpcs.2018.04.043. |
(Author Not Attending)
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A02.00004: Detecting quantum phase transitions in the Kitaev model through topological entanglement entropy. Adu Vengal, David Ronquillo, Nandini Trivedi We use exact diagonalization on up to 16 site clusters to investigate the isotropic point of the Kitaev honeycomb model under an applied magnetic field. Using the Kitaev-Preskill construction, we calculate the topological entanglement entropy (TEE), as a function of both the field strength and field orientation. We detect distinct anomalies in the TEE which are indicative of quantum phase transitions to and from the field induced gapped quantum spin liquid (QSL) phase, a new gapless intermediate QSL, and the higher field partially polarized phase. These results are corroborated by corresponding level crossings in the energy spectrum. |
Friday, September 28, 2018 2:30PM - 2:45PM |
A02.00005: Percolation through Porous Media comprised of Axially Symmetric Grains Donald Priour The permeability of porous materials to fluid or charge flow is of fundamental and industrial relevance. The density of impenetrable grain or inclusions making up a medium determines if fluid flow occurs on large scales or if transport is not possible in the bulk limit. In the thermodynamic limit, the shift with increasing grain concentration between the former and latter scenarios is known as a percolation transition. In the case of fluid flow through irregular spaces between impenetrable grains, percolation phenomena are a class of continuum percolation known as void percolation. With a dynamic infiltration algorithm in which statistics are accumulated on virtual tracer particles navigating spaces between inclusions to find the critical grain concentration ρc, we have calculated percolation thresholds for randomly placed and randomly oriented axially symmetric grains for broad range of aspect ratios (from highly oblate plate-like to highly prolate needle-like inclusions), for a variety of shapes. Critical concentrations for the latter (including, e.g., ellipsoids, cylinders, and cones) appear to converge to a common geometry independent asymptotic value in the large aspect ratio limit. |
Friday, September 28, 2018 2:45PM - 3:00PM |
A02.00006: Electron- Phonon Relaxation Dynamics of Thiolate-Protected Plasmonic Gold Clusters Masoud Shabaninezhad Navrood The influence of passivating ligand on electron-phonon (e-p) relaxation dynamics of smallest sized gold clusters was studied using ultrafast transient absorption spectroscopy and theoretical modeling. The e-p relaxation of Au279, Au329 and Au333 passivated with tertiary butyl benzene thiol (TBBT), Phenyl ethane thiol (SC2Ph) and hexane thiol (SC6), respectively, were investigated. These clusters were chosen as they were the smallest gold clusters (till date) that show plasmonic properties and the sizes are similar but with different passivating ligands. Furthermore, to compare the electron dynamics of ligand-free and ligand-conjugated samples, optical properties of citrate stabilized Au NPs with d=13 nm were studied. The results show that all investigated clusters are plasmonic via power-dependent surface plasmon bleach recovery kinetics except that of Au329 (SC2Ph), which has shown smaller power dependence. Also, the results show that the ligands do influence the intrinsic e-p coupling time and e-p coupling strength. To model the effect of ligands, free electron density (n) reduction of all samples was obtained using three-layered Mie theory and the results show that SC6 interacts least with core-gold while TBBT and SC2Ph has greater effect on the surface electron conductivity. |
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