Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session H06: Frustrated Lattices: Kitaev, Pyrochlore, and Others |
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Sponsoring Units: DCMP GMAG Chair: Stephen Winter, Goethe University Frankfurt Room: BCEC 109A |
Tuesday, March 5, 2019 2:30PM - 2:42PM |
H06.00001: Intermediate gapless phase and topological phase transition of the Kitaev model in a uniform magnetic field Shuang Liang, Ming-Hong Jiang, Wei Chen, Jian-Xin Li, Qiang-Hua Wang We study the Kitaev model in a [001] magnetic field employing the mean-field theory(MFT) in the Majorana fermion representation. We discover a robust gapless regime in the intermediate magnetic field for both gapless and gapped antiferromagnetic(AFM) Kitaev models with Jx = Jy before the system is polarized in a high magnetic field. A topological phase transition connecting two gapless phases with a nodal line phase takes place at a critical magnetic field h_{c1} in this regime. While the nodal line phase at h_{c1} disappears when the mirror symmetry Jx = Jy is broken, the nodal point gapless phase can exist at intermediate fields even without the mirror symmetry. We reveal that the phase evolution of the system in the magnetic field is driven by the competition between the magnetic field and the particle-hole asymmetry of the normal state of the BdG Hamiltonian. For the ferromagnetic case, there is no intermediate phase transition before polarization. The above phase diagrams are confirmed by dynamical MFT results. |
Tuesday, March 5, 2019 2:42PM - 2:54PM |
H06.00002: Majorana representations of spin and an alternative solution of the Kitaev honeycomb model Jianlong Fu, Johannes Knolle, Natalia Perkins Based on the Dirac spinor representation of the SO(4) group, we discuss the relationship between three types of representation of spin in terms of Majorana fermions, namely the Kitaev representation, the SO(3) representation, and the SO(4) chiral representation. Comparing the three types, we show that the Hilbert space of the SO(3) representation is different from the other two by requiring a pairing of sites, but it has the advantage over the other two in that no unphysical states are involved. As an example of its application, we present an alternative solution of the Kitaev honeycomb model. Our solution involves no unphysical states which enables a systematic calculation of physical observables. Finally, we discuss an extension of the model to a more general exactly soluble Z_{2} gauge theory interacting with complex fermions. |
Tuesday, March 5, 2019 2:54PM - 3:06PM |
H06.00003: Algebraic Quantum Spin Liquid from an Exactly Solvable Spin-1/2 Kitaev Model Jian-Jian Miao, Hui-Ke Jin, Fu-Chun Zhang, Yi Zhou We propose an exactly solvable quantum spin-1/2 model with time reversal invariance on a two dimensional brick-wall lattice, where each unit cell consists of three sites. We find that the ground states are algebraic quantum spin liquid states. The spinon excitations are gapless and the energy dispersion is linear around two Dirac points. The ground states are of three-fold topological degen- |
Tuesday, March 5, 2019 3:06PM - 3:18PM |
H06.00004: Topological superconductivity in the Kondo-Kitaev model Wonjune Choi, Philipp Wilhelm Klein, Achim Rosch, Yong-Baek Kim We investigate possible topological superconductivity in the Kondo-Kitaev model on the honeycomb lattice, where the Kitaev spin liquid is coupled to conduction electrons via the Kondo coupling. The self-consistent mean-field theory gives three distinct quantum phases as the Kondo coupling is increased: the fractionalized Fermi liquid, where the Kitaev spin liquid and conduction electrons remain decoupled, the ferromagnetic topological superconductor with a single chiral Majorana edge mode, and the paramagnetic topological superconductor with a single pair of helical Majorana edge modes. In this talk, we discuss the connection between topological nature of the Kitaev spin liquid and two emergent topological superconductors obtained in this model. These findings offer a novel route to topological superconductivity in the Kondo lattice system. |
Tuesday, March 5, 2019 3:18PM - 3:30PM |
H06.00005: Emergent interacting two-fluids in a disordered Hubbard model Kyungmin Lee, Aavishkar Patel, Nandini Trivedi, Subir Sachdev Recently a number of theoretical studies of models containing lattices of Sachdev-Ye-Kitaev (SYK) islands have brought in a fresh perspective on the problem of non-Fermi liquids. Motivated especially by a two-fluid model, with localized SYK islands and itinerant fermions, that captures the physics of the ``strange’’ metal state of high temperature superconductors, here we discuss the possibility of such a separation of fermionic degrees of freedom starting from a disordered Hubbard model. Our numerical studies indicate that a disordered Hubbard model can lead to the emergence of localized SYK-like islands that interact with itinerant fermions. We also discuss the implications of disorder of the temperature-dependent transport properties. |
Tuesday, March 5, 2019 3:30PM - 3:42PM |
H06.00006: Many-body localization in a modified SYK model Hanteng Wang, Alex Kamenev We investigate the many-body spectrum and eigenfunctions of Sachdev-Ye-Kitaev model with additional random hopping terms. To preserve the symmetry class of the original model, the additional term we add is the square of standard two Majorana hopping which is integrable on its own. We examine the level statics of the many-body energy spectrum of this model numerically and find the crossover from Poisson statistics to Wigner-Dyson statistics when tuning the total energy of the system with finite number of Majorana. We study relations of the transition in level statistical transition to Anderson localization in the Fock space by examining the inverse partition ratios (IPR) and information entropy of the eigenstates with different total energy. Fitting IPR and information entropy with a scaling ansatz, one can access degree of the Fock space localization of the many-body eigenstates. We found that there exist three different regimes: ergodic delocalized, non-ergodic delocalized and localized, which closely resembles findings for the Anderson model on Bethe lattice and random regular graphs. |
Tuesday, March 5, 2019 3:42PM - 3:54PM |
H06.00007: Strong impact of all-in all-out magnetic order on magnetic and lattice dynamics in pyrochlore iridates studied by Raman spectroscopy Kentaro Ueda, Ryoma Kaneko, Alaska Subedi, Matteo Minola, Bumjoon Kim, Jun Fujioka, Yoshinori Tokura, Bernhard Keimer We perform Raman spectroscopy on pyrochlore Eu2Ir2O7 which undergoes a paramagnetic-to-antiferromagnetic transition, as well as paramagnetic counterpart Pr2Ir2O7. |
Tuesday, March 5, 2019 3:54PM - 4:06PM |
H06.00008: Linear magnetoresistance in the all-in-all-out antiferromagnet Cd_{2}Os_{2}O_{7} Yishu Wang, Yejun Feng, Felipe Gomez, Daniel Silevitch, Jiaqiang Yan, David George Mandrus, Patrick Lee, Thomas F Rosenbaum The pyrochlore Cd_{2}Os_{2}O_{7} undergoes a metal-insulator transition at 227 K, concomitant with a formation of all-in-all-out magnetic ordering. Here, we explore the magnetoresistance associated with this magnetic order, which manifests an odd-parity linear functional form. This form, recently reported in the related compounds Eu_{2}Ir_{2}O_{7}, is allowed by the Onsager relationship for antiferromagnetic materials; however the microscopic origin is still unclear. By systematically studying a range of galvanomagnetic measurement configurations, we are able offer potential mechanisms for understanding this linear magnetoresistance involving transport both in the bulk and along the magnetic domain walls. |
Tuesday, March 5, 2019 4:06PM - 4:18PM |
H06.00009: Visualizing Kondo lattice behavior in the frustrated pyrochlore iridate Pr_{2}Ir_{2}O_{7} using scanning tunneling spectroscopy and machine learning Mariam Kavai, Kyle G Sherman, Justin Leshen, Joel Friedman, Ioannis Giannakis, Satoru Nakatsuji, Michael J Lawler, Pegor Aynajian Pyrochlore iridates have attracted great interest due to their geometrically frustrated lattice with potential for realizing metallic spin liquid behavior. Pr_{2}Ir_{2}O_{7} is uniquely located near the quantum critical point of antiferromagnetic metal to insulator transition. We carried out STM experiments on the [111] Kagome surface of the pyrochlore iridate Pr_{2}Ir_{2}O_{7}. STM topographs show the six-fold atomic structure expected from the [111] surface demonstrating atomic resolution STM images on a pyrochlore iridate. At low temperature, the tunneling density of states reveal Kondo behavior with Fano lineshape near the Fermi energy that exhibit strong electronic inhomogeneity. The large quantity of generated data and the intrinsic electronic inhomogeneity in this system introduce enough complexity to render conventional data analysis inadequate. Using machine learning of large data, we discover these rather seemingly random spectra to form nanoscale patterns, which may be related to electronic entanglement. |
Tuesday, March 5, 2019 4:18PM - 4:30PM |
H06.00010: Using quantum typicality to compute the thermodynamics of the frustrated spin compound SrCu2(BO3)2 Alexander Wietek, Andreas Honecker, Philippe Corboz, Stefan Wessel, Frederic Mila, Bruce Normand The concept of quantum typicality presents a novel route to computing finite temperature |
Tuesday, March 5, 2019 4:30PM - 4:42PM |
H06.00011: Partial order in the extended Hubbard model on a triangular lattice Matthew Enjalran The list of new materials which possess charge, spin, and orbital degrees |
Tuesday, March 5, 2019 4:42PM - 4:54PM |
H06.00012: Supersymmetry in an interacting Majorana model on the kagome lattice Chengshu Li, Étienne Lantagne-Hurtubise, Marcel Franz We construct a supersymmetric model of interacting Majorana modes on the kagome lattice. The supersymmetry is manifest in the infinite-coupling limit, which exhibits an exponential ground state manifold separated in two parity "supersectors". An exact solution for thin torus geometries allows us to analytically construct the entire ground state manifold. Upon inclusion of weak two-fermion terms, the supersymmetry is broken for finite systems but recovered in the thermodynamic limit. We also briefly discuss the non-interacting limit of the model, which exhibits a zero-energy flat band and Majorana Chern bands. |
Tuesday, March 5, 2019 4:54PM - 5:06PM |
H06.00013: Majorana-Hubbard model on the triangular lattice Tarun Tummuru, Alberto Nocera, Ian Affleck Majorana fermions are known to arise as emergent particles in certain condensed matter systems. One such realization involves inducing superconductivity on the surface of a 3-dimensional topological insulator, in the presence of a magnetic field. The resulting Abrikosov lattice has a Majorana zero mode (MZM) localized at the core of each vortex. It has been shown that the interaction between MZMs falls off exponentially with the superconducting coherence length. This enables one to write a tight-binding model to describe the system and some of these models have rich phase diagrams that exhibit emergent supersymmetry. Given that in experiments the vortex lattice usually has a triangular geometry, we construct a model for interacting MZMs in this setup. With the interaction strength as a tunable parameter, we study the phase diagram numerically using the density-matrix renormalization group. |
Tuesday, March 5, 2019 5:06PM - 5:18PM |
H06.00014: Possible gapless spin liquid in a rare-earth kagome lattice magnets Tm_{3}Sb_{3}Zn_{2}O_{14} Zhaofeng Ding, Yanxing Yang, Jian Zhang, Cheng Tan, Zihao Zhu, Gang Chen, Lei Shu We report the thermodynamic and muon spin relaxation (μSR) evidences for a possible gapless spin liquid in Tm_{3}Sb_{3}Zn_{2}O_{14}, with the rare-earth ions Tm^{3+} forming a two-dimensional kagome lattice. We extract the magnetic specific heat of Tm_{3}Sb_{3}Zn_{2}O_{14} by subtracting the phonon contribution of the non-magnetic isostructural material La_{3}Sb_{3}Zn_{2}O_{14} and obtain a clear linear-T temperature dependence of magnetic specific heat at low temperatures. The absence of magnetic order is confirmed by specific heat, A.C. susceptibility and μSR measurements down to 20 mK. We find that the spin-lattice relaxation time remains constant down to the lowest temperature. The possibility of disorder induced effect could not be excluded duo to the possible Tm/Zn site-mixing disorder in Tm_{3}Sb_{3}Zn_{2}O_{14}. |
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