Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session R45: Reduced Dimensionality 
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Sponsoring Units: DCMP Chair: Fereshte Ghahari, NIST/University of Maryland, College Park Room: LACC 505 
Thursday, March 8, 2018 8:00AM  8:12AM 
R45.00001: Phase Transitions and Magnetic Ordering in the 1D Hubbard Chain Randy Sawaya, Natalia Chepiga, Steven White The phase transitions and magnetic ordering of the one dimensional spin1/2 Hubbard chain are studied as a function of the next nearest neighbor hopping and onsite interaction using DMRG. At large U, this model maps to a MajumdarGhosh chain with known KosterlitzThouless transition(KT point) at J_{2}/J_{1} ∼ 0.2411 and commensurateincommensurate transition(Disorder(DO) point) at J_{2}/J_{1} = 0.5, prompting the investigation of such points within the lowU limit. Extending the methods used in Heisenberg spin chains to the Hubbard model, the velocity as well as the central charge are calculated for different values of t_{2} and U in order to deduce the KT point. Similarly, the spin correlation function 〈S_{N/2 + 1} S_{i + N/2 + 1}〉 is found and fitted to the dimerized OrnsteinZernicke form to determine the correlation length, with the location of the minimum indicating the DO point. Preliminary analysis for U = 4 shows a KT point at t_{2}/t_{1} ∼ 0.564 and a DO point at t_{2}/t_{1} ∼ 0.68. Future work will include an extensive study of the migration of these points as a function of U. 
Thursday, March 8, 2018 8:12AM  8:24AM 
R45.00002: A Temperature Driven Holephonon Coupling Enhancement Effect in a Strongly Correlated 2D Hole System Shuhao Liu, ChiehWen Liu, Arvind Shankar, Loren Pfeiffer, K West, Xuan Gao In strongly correlated 2D electron/hole system confined in semiconductor heterointerfaces, a pronounced nonmonotonic behavior in the resistivty vs. temperature, ρ(T), has been widely observed when the system becomes quantum degenerate but no consensus has been reached regarding its origin. Here we report a study of the the holephonon coupling strength around the peak temperature T_{p }of the nonmonotonic ρ(T) in a dilute 2D hole system with strong correlations by measuring the hot hole energy relaxation rate. The data can be well fitted by BlochGrüneisen theory of holephonon scattering but the deformational potential constant D shows a rapid change near T_{P} (around 6eV12eV at high temperatures, T~T_{F}, the Fermi temperature, and around 3080eV at low temperatures, T<<T_{F}). We suggest that these results could be related to the system being close to the transition into Wigner crystal state and compare them to the strong electronphonon coupling effect in charge density wave states. 
Thursday, March 8, 2018 8:24AM  8:36AM 
R45.00003: Duality and universal transport in mixeddimension electrodynamics WeiHan Hsiao, Dam Son We consider a theory of a twocomponent Dirac fermion localized on a (2+1)dimensional brane coupled to a (3+1)dimensional bulk. Using the fermionic particlevortex duality, we show that the theory has a strongweak duality that maps the coupling e to (8π)/e. We explore the theory at e^{2} = 8π where it is selfdual. The electrical conductivity of the theory is a constant independent of frequency. When the system is at finite density and magnetic field at filling factor ν=1/2 , the longitudinal and Hall conductivity satisfies a semicircle law, and the ratio of the longitudinal and Hall thermal electric coefficients is completely determined by the Hall angle. The thermal Hall conductivity is directly related to the thermal electric coefficients. 
Thursday, March 8, 2018 8:36AM  8:48AM 
R45.00004: Odd viscosity in two dimensional incompressible fluids Sriram Ganeshan, Alexander Abanov, Tankut Can In everyday fluids, the viscosity is resistance to flow and is dissipative, but a quantum Hall (QH) fluid at zero temperature has nondissipative viscosity dubbed `oddviscosity'. In this talk, I will present observable consequences of parityviolating odd viscosity term in incompressible 2+1D hydrodynamics. For boundary conditions depending on the velocity field (flow) alone we show that: (i) The fluid flow quantified by the velocity field is independent of odd viscosity, (ii) The force acting on a closed contour is independent of odd viscosity, and (iii) The odd viscosity part of torque on a closed contour is proportional to the rate of change of area enclosed by the contour with the proportionality constant being twice the odd viscosity. The last statement allows us to define a measurement protocol of "odd viscostance" in analogy to Hall resistance measurements. We also consider nostress boundary conditions which explicitly depend on odd viscosity. I will discuss effects of odd viscosity in classic hydrodynamics problems with nostress boundary conditions, namely, bubble in a planar Stokes flow and surface gravity waves. 
Thursday, March 8, 2018 8:48AM  9:00AM 
R45.00005: Quasiparticle decay in a onedimensional BoseFermi mixture Benjamin Reichert, Aleksandra Petković, Zoran Ristivojevic In the past 20 years, the developpement of highly controlled experimental setups of ultradcold atoms has opened new ways of investigating lowdimensional mixtures of quantum fluids. In particular, one can realize BoseFermi mixtures (BFM) where the physical properties of the system can be probed at arbitrary coupling strength through Feshbach resonance. The usual starting point for the theoretical description of onedimensional BFM is done in terms of a twocomponent Luttinger liquid. Although this lowenergy approach can succesfully describe various phenomena, it fails at describing the decay rate of excitations. 
Thursday, March 8, 2018 9:00AM  9:12AM 
R45.00006: Channeldecomposed solution of the parquet equations in the twodimensional Hubbard model Christian Eckhardt, Giulio Schober, Carsten Honerkamp The parquet equations are a set of selfconsistent equations for the effective interaction vertex of an interacting manyfermion system. The application of the parquet equations in bulk models is however complicated by the complex emergent momentum and frequency structure of the vertex. Here we show how channeldecomposition techniques for the treatment of the momentum dependence that were developed in the context of the functional renormalization group can be applied to the parquet equations. We describe solutions using this technique for the halffilled Hubbard model on the square lattice and discuss generalizations to other cases, as well as ways to include the frequency dependence of the vertices. 
Thursday, March 8, 2018 9:12AM  9:24AM 
R45.00007: The role of electronelectron interactions in twodimensional Dirac fermions Shaffique Adam, Ho Kin Tang, Jia Ning Leaw, João Rodrigues, Pinaki Sengupta, Igor Herbut, Fakher Assaad The role of electronelectron interactions on twodimensional Dirac fermions remains enigmatic. Using a combination of nonperturbative numerical and analytical techniques that incorporate both the contact and longrange parts of the Coulomb interaction, we identify the two previously discussed regimes: a GrossNeveu transition to a strongly correlated Mott insulator, and a semimetallic state with a logarithmically diverging Fermi velocity accurately described by the random phase approximation. Most interestingly, experimental realizations of Dirac fermions span the crossover between these two regimes providing the physical mechanism that masks this velocity divergence. We explain several longstanding mysteries including why the observed Fermi velocity in graphene is consistently about 20 percent larger than the best values calculated using ab initio and why graphene on different substrates show different behavior. 
Thursday, March 8, 2018 9:24AM  9:36AM 
R45.00008: Symmetry and duality in bosonization of twodimensional Dirac fermions David Mross, Jason Alicea, Olexei Motrunich Threedimensional topological insulators famously host a single Dirac cone of nearly free electrons at their surface. Recent work has shown that this weaklyinteracting Dirac liquid may be equivalently described as a stronglycorrelated liquid of ‘dual’ Dirac fermions coupled to an emergent photon, or by selfdual bosons coupled to a ChernSimons gauge field. I will present an exact mapping that implements these dualities in concrete models, focusing on the realization of symmetries for the various degrees of freedom, i.e., bosons, vortices, fermions and fermionic vortices. In addition, I will describe an interesting ‘modular’ structure that arises in the case of powerlaw interactions. 
Thursday, March 8, 2018 9:36AM  9:48AM 
R45.00009: Title: Classification of Floquet drives of onedimensional fermions. Abhishodh Prakash, Lukasz Fidkowski One of the recent developements in condensed matter is the idea that there can exist new phases of matter in periodically driven Floquet systems that are absent in equilibrium. In the presence of global symmetries, it was shown by von Keyserlingk et al. that we could have new symmetryprotectedtopological (SPT) phases characterized by the existence of robust ‘pumped’ boundary modes that are absent in equilibrium. Roy and Harper provided an alternative perspective on these phases in terms of a classification of loopunitaries (time evolution operators of the form U(t) U(0) = U(T) = 1). From this point of view, the FloquetSPT phases that are unique to the driven setting are those that correspond to loopunitaries that cannot be deformed to a trivial one (U(t) = 1) without breaking symmetry. In this work, we use Roy and Harper's scheme to study how the classification of driven one dimensional freefermion phases for the different AltlandZirnbauer symmetry classes changes in the presence of interactions. We find our results to be in agreement with those obtained by von Keyserlingk et al. 
Thursday, March 8, 2018 9:48AM  10:00AM 
R45.00010: Density Matrix Renormalization Group Study of One Dimensional Models Beyond the BornOppenheimer Approximation Mingru Yang, Steven White We study one dimensional models of molecules and solids where both the electrons and nuclei are treated as quantum particles, going beyond the usual BornOppenheimer approximation. The continuous system is approximated by a grid which computationally resembles a ladder, with the electrons living on one leg and the nuclei on the other. To simulate DMRG well with this system, a threesite algorithm has been implemented. We also use a compression method to treat the longrange interactions between charged particles. We find that 1D diatomic molecules ("H2") with spin1/2 nuclei in the spin triplet state will unbind when the mass of the nuclei reduces to only a few times larger than the electron mass. The molecule with nuclei in the singlet state always binds. The case of spin0 bosonic nuclei is investigated as well. 
Thursday, March 8, 2018 10:00AM  10:12AM 
R45.00011: Quantum Loops, an Infinite Hierarchy of Multicritical Points in 2+1D. Zhehao Dai, Adam Nahum Quantum loop emergent from spin system realizes strongly interacting states. We report a series of critical systems where fluctuation of deconfined large loops give qualitatively new phenomena  topologically constrained dynamics of loops determines lowenergy excitation; topologically different ways to reconnect loops dictates operator contents. Interestingly, these states also exhibit a rich structure of unusual ground state degeneracy below the continuous gapless spectrum, generalizing the topological degeneracy in gapped systems and Anderson tower in gapless systems. In particular, we report a special case realizing multicritical point between Z2trivial and Z2SPT phases in 2+1D. 
Thursday, March 8, 2018 10:12AM  10:24AM 
R45.00012: A Numerical Study of a Disorderdriven 2D Mott InsulatortoMetal Quantum Phase Transition Jared O'Neal, Zhenyu Wang, Yoshinori Okada, Vidya Madhavan, Nandini Trivedi

Thursday, March 8, 2018 10:24AM  10:36AM 
R45.00013: Dual Fermions Study of the 2D Hubbard Model Joseph Paki, James LeBlanc, Emanuel Gull The Hubbard model is believed to contain strongly correlated physics relevant to high temperature superconductors. As in the holedoped cuprates, the Hubbard model's phase diagram includes a superconducting dome below a pseudogap phase that is characterized by a momentum selective suppression of low energy excitations. Numerical studies of this phase thus require high resolution in both momentum and energy in order to resolve the details of the Fermi surface, which is challenging with numerical methods like dynamical mean field theory and its cluster extensions. In this work we apply the recently developed dual fermions technique to study the spectral function at high resolution in $k$ and $\omega$. We extract properties of the electronic structure in the high temperature regime of the 2D Hubbard model, analytically continued to real frequencies, and study the onset and evolution of the momentum selective behavior for variation in model parameters. 
Thursday, March 8, 2018 10:36AM  10:48AM 
R45.00014: The global phase diagram of the 1D SYK model with finite N Xin Dai, Shaokai Jian, Hong Yao We study the generalized SYK model on a 1D lattice with $N$ fermions on each SYK sites and random quadratic coupling between SYK sites. 
Thursday, March 8, 2018 10:48AM  11:00AM 
R45.00015: Stable 1d nonFermi liquids and lattice theory Chaitanya Murthy, Chetan Nayak, Michael Freedman

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