Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session E44: Design of Correlated Electron Materials |
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Sponsoring Units: DCMP Chair: Theo Siegrist, NHMFL-FSU Room: LACC 504 |
Tuesday, March 6, 2018 8:00AM - 8:12AM |
E44.00001: Correlated Materials Design: Prospects and Challenges Ran Adler, Chang-Jong Kang, chuck yee, Gabriel Kotliar The design of correlated materials challenges researchers to combine the |
Tuesday, March 6, 2018 8:12AM - 8:24AM |
E44.00002: Critical role of electronic correlations in determining crystal structure of transition metal compounds Tsung-Han Lee, Yong-Xin Yao, Vladan Stevanovic, Vladimir Dobrosavljevic, Nicola Lanata The choice that a solid system "makes" when adopting a crystal structure (stable or metastable) is ultimately governed by the interactions between electrons forming chemical bonds. By analyzing 6 prototypical binary transition-metal compounds we demonstrate here that the orbitally-selective strong d-electron correlations influence dramatically the behavior of the energy as a function of the spatial arrangements of the atoms. Remarkably, we find that the key physical mechanism underlying this complex behavior can be traced back to simple electrostatics, i.e., to the fact that the strong d-electron correlations influence substantially the charge transfer mechanism, which, in turn, controls the electrostatic interactions. This result advances our understanding of the influences of strong correlations on the crystal structure, opens a new avenue for extending structure prediction methodologies to strongly correlated materials, and paves the way for predicting and studying metastability and polymorphism in these systems. |
Tuesday, March 6, 2018 8:24AM - 8:36AM |
E44.00003: Emergent Phases of Fractonic Matter Abhinav Prem, Michael Pretko, Rahul Nandkishore Fractons are emergent particles which are immobile in isolation, but which can move together in dipolar pairs or other small clusters. These exotic excitations naturally occur in certain quantum phases of matter described by tensor gauge theories. While previous research has focused on the properties of small numbers of fractons and their interactions, in this work we consider systems with a finite density of either fractons or their dipolar bound states. We study some of the phases in which emergent fractonic matter can exist, thereby initiating the study of the "condensed matter" of fractons. We begin by considering a system with a finite density of fractons, which we show can exhibit microemulsion physics, in which fractons form small-scale clusters emulsed in a phase dominated by long-range repulsion. We then study systems with a finite density of mobile dipoles and focus on two examples: Fermi liquids and quantum Hall phases. A finite density of fermionic dipoles will form a Fermi surface and enter a Fermi liquid phase. This dipolar Fermi liquid exhibits a finite-temperature phase transition, corresponding to an unbinding transition of fractons. Finally, we study chiral two-dimensional phases corresponding to dipoles in "quantum Hall" states of their emergent magnetic field. |
Tuesday, March 6, 2018 8:36AM - 8:48AM |
E44.00004: Uncovering the Origin of Divergence in the CsM(CrO_{4})_{2} (M = La, Pr, Nd, Sm; Am) Family through Examination of the Chemical Bonding in a Molecular Cluster and by Band Structure Analysis Shane Galley, Alexandra Arico, Tsung-Han Lee, Yong-Xin Yao, Xiaoyu Deng, Joseph Sperling, Vanessa Proust, Julia Storbeck, Vladimir Dobrosavljevic, Thomas Albrecht-Schmitt, Nikolas Kaltsoyannis, Nicola Lanata A series of f-block chromates, CsM(CrO_{4})_{2} (M = La, Pr, Nd, Sm; Am), were prepared revealing notable differences between the Am^{III} derivative and its lanthanide analogs. While all compounds form similar layered structures, the americium compound exhibits polymorphism and adopts both a structure isomorphous with the early lanthanides as well as one that possesses lower symmetry. Both polymorphs are dark red and possess band gaps that are smaller than the Ln^{III} compounds. In order to probe the origin of these differences, the electronic structure of α-CsAm(CrO_{4})_{2} was determined computationally using both a molecular cluster approach featuring hybrid density functional theory and QTAIM analysis and by the periodic LDA+GA method. Taken together, these complementary methods demonstrate that while there is Am-O covalency in α-CsAm(CrO_{4})_{2}, it is driven by the degeneracy of the 5f and 2p orbitals and not by orbital overlap. |
Tuesday, March 6, 2018 8:48AM - 9:00AM |
E44.00005: Organizing symmetry-protected topological phases by layering and symmetry forgetting: a minimalist perspective Zhaoxi Xiong, Aris Alexandradinata It is demonstrated that fermionic/bosonic symmetry-protected topological (SPT) phases across different dimensions and symmetry classes can be organized using geometric constructions that increase dimensions and symmetry-forgetting maps that change symmetry groups. Specifically, it is shown that the interacting classifications of SPT phases with and without glide symmetry fit into a short exact sequence, so that the classification with glide is constrained to be a direct sum of cyclic groups of order 2 or 4. Applied to fermionic SPT phases in the Wigner-Dyson class AII, this implies that the complete interacting classification in the presence of glide is ${\mathbb Z}_4 \oplus {\mathbb Z}_2 \oplus {\mathbb Z}_2$ in 3 dimensions. In particular, the hourglass-fermion phase recently realized in the band insulator KHgSb must be robust to interactions. Generalizations to spatiotemporal glide symmetries are discussed. |
Tuesday, March 6, 2018 9:00AM - 9:12AM |
E44.00006: Layer Construction of Floquet Topological Phases Fenner Harper, Rahul Roy Periodically driven systems can exhibit anomalous transport at the boundary of an open system, even when the bulk (quasienergy) bands are topologically trivial. We introduce a layer construction for Floquet phases without symmetry that is applicable to any even spatial dimension. This allows topologically nontrivial phases to be constructed from class AIII Hamiltonians in one lower dimension. This construction has the advantage that along one dimension it requires only nearest-neighbour interactions, making the resulting models particularly suitable for experimental realisations involving synthetic dimensions. We motivate the layer construction in the context of free fermions, and go on to discuss its applicability to interacting systems. |
Tuesday, March 6, 2018 9:12AM - 9:24AM |
E44.00007: A simple computational tool to investigate strongly correlated system Godfrey Akpojotor, Myron Williams Echenim, Famous Akpojotor Most often, the mathematical and computational tools to investigate strongly correlated systems are complex, thereby making it difficult to following the research in this field of correlated electrons which represents the frontier of our understanding of the electronic and magnetic properties of solids. It is therefore necessary to develop a simplified computational tool for few particles to give useful insight into these strongly correlated systems. The purpose of this study is to extend our algorithmic formulation of a highly simplified correlated variational approach (HSCVA) for strongly correlated two electrons on many sites in all three dimensions to many electrons on many sites in all three dimensions within a t-U-V-J model. The parameter space for obtaining partial polarization, full polarization and mixed states which is a possible signature for superconductivity are delineated within this model. The implication for a number of strongly correlated materials is discussed. |
Tuesday, March 6, 2018 9:24AM - 9:36AM |
E44.00008: Analytic Continuation-Free Green's Function Approach to Correlated Electronic Structure Calculations Andreas Oestlin, Levente Vitos, Liviu Chioncel We present a charge self-consistent scheme combining density functional and dynamical mean field theory, which uses Green's functions of multiple-scattering type. In this implementation, the many-body effects are incorporated into the Kohn-Sham iterative scheme without the need for the numerically ill-posed analytic continuation of the Green's function and of the self-energy, which was previously a bottleneck in multiple-scattering-type Green's function approaches. The current implementation improves on numerical accuracy, compared to previous implementations where analytic continuation was required at each Kohn-Sham self-consistent step. A minimal effort aside from the multiple-scattering formulation is required, and the method can be generalized in several ways that are interesting for applications to real materials.^{11)}A. Östlin, L. Vitos, and L. Chioncel, Phys. Rev. B 96, 125156 (2017) |
Tuesday, March 6, 2018 9:36AM - 9:48AM |
E44.00009: Fermi surface reconstructions and transport spectroscopy in heavy-fermion materials Gertrud Zwicknagl, A. Pourret, S. G. Sharapov, T. D. Matsuda, G. Knebel, A. A. Varlamov Fermi surface (FS) reconstructions lead to pronounced anomalies in thermodynamic and transport properties of heavy-fermion materials. Of particular interest are Electronic Topological (Lifshitz) transitions where the number of FS sheets changes abruptly under the influence of external parameters like chemical doping, pressure, or magnetic field. Lifshitz transitions are generally associated with the presence of critical points in the electronic band structure. |
Tuesday, March 6, 2018 9:48AM - 10:00AM |
E44.00010: Strongly Correlated Metal built from Sachdev-Ye-Kitaev Models Xueyang Song, Chao-ming Jian, Leon Balents Prominent systems like high Tc cuprates and heavy fermions display intriguing features going beyond the quasiparticle description. The Sachdev-Ye-Kitaev(SYK) model provides a powerful framework to study such physics. It describes a 0+1D quantum cluster with random all-to-all \emph{four}-fermion interactions among N Fermion modes which becomes exactly solvable as N→∞, exhibiting a zero-dimensional non-Fermi liquid with emergent conformal symmetry and complete absence of quasi-particles. Here we study a lattice of complex-fermion SYK dots with random inter-site \emph{quadratic} hopping. Combining the imaginary time path integral with \emph{real} time path integral formulation, we obtain a heavy Fermi liquid to incoherent metal crossover in full detail, including thermodynamics, low temperature Landau quasiparticle interactions, and both electrical and thermal conductivity at all scales. We find linear in temperature resistivity in the incoherent regime, and a Lorentz ratio L≡κρT varies between two universal values as a function of temperature. Our work exemplifies an analytically controlled study of a strongly correlated metal. |
Tuesday, March 6, 2018 10:00AM - 10:12AM |
E44.00011: Approximation of the Sachev-Ye-Kitaev Model by Free Fermion Variational States Daniel Ish, Mark Srednicki The Sachdev-Ye-Kitaev model is a zero dimensional model of fermions subject to fully random two fermion interactions. This model has been of considerable interest in both the condensed matter and high energy communities, primarily due to its emergent conformal symmetry in the thermodynamic limit. Strangely, in this limit, the fermion correlators of this model also satisfiy Wick's Theorem, suggesting that there is something "free" about this highly interacting model. Motivated by this observation, we use the Gibbs-Delbruck variational principle to numerically compute the closest free approximation to a ground state or thermal density matrix of a sample of the Sachdev-Ye-Kitaev ensemble. Despite a rich structure to these free fermion approximations, we find that they are exceedingly poor approximations on average in the thermodynamic limit. Some discussion will also be given on how to reconcile this fact with the previously mentioned properties of the free fermion correlators. |
Tuesday, March 6, 2018 10:12AM - 10:24AM |
E44.00012: Evaluation of Fermi surfaces, single and two-particle spectral properties for FeSe using Quasi-particle self consistent GW + DMFT Swagata Acharya, Dimitar Pashov, Mark van Schilfgaarde Most of the first principles techniques, based on DFT or DFT+DMFT frameworks, fails to reproduce the spectral properties of the FeSe both in the tetragonal and orthorhombic phases. Within our recently developed quasi-particle self-consistent GW coupled to DMFT, we show how proper estimations of the non-local fluctuations and local spin fluctuations reproduce the spectral properties in very good agreement with the experiments. We also compute the spin-wave excitation spectra and find momentum dependent shifts in spin-fluctuation weights across the structural transition at 90 K. We rigorously show how these compare with the extant experimental findings. |
Tuesday, March 6, 2018 10:24AM - 10:36AM |
E44.00013: Anyonic Excitations of Hardcore Anyons Julia Wildeboer, Sourav Manna, Anne Nielsen In this talk, we show that not only strongly interacting many-body systems consisting of fermions or bosons can host exotic quasi-particles with anyonic statistics with unusual properties, but also systems of anyons themselves can give rise to |
Tuesday, March 6, 2018 10:36AM - 10:48AM |
E44.00014: Fidelity Mechanics: Analogues of the Four Thermodynamic Laws and Landauer's Principle Huan-Qiang Zhou Fidelity mechanics, a scheme to investigate critical phenomena in quantum many-body physics, is formulated as an analogue of the four laws in thermodynamics and black hole mechanics, thus unveiling a formal connection between critical points and black holes. |
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