4,674 research outputs found

    Topological-Fermi-Liquid to Quantum-Hall-Liquid Transitions: pp-Band and dd-Band Fermions in a Magnetic Field

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    We find that in a multi-orbital system with intraorbital and interorbital hopping integrals, the Hall conductance exhibits various topological quantum phase transitions (QPTs) induced by on-site orbital polarization: integer quantum Hall (IQH) plateau transitions, and topological Fermi liquid to IQH transitions. Such topological QPTs are demonstrated in two systems: a pp-band spinless fermionic system realizable with ultracold atoms in optical lattice, and a dd-band spinful fermionic system closely related to giant orbital Hall effects in transition metals and their compounds.Comment: 4 pages, 4 figure

    Edge States and Quantum Hall Effect in Graphene under a Modulated Magnetic Field

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    Graphene properties can be manipulated by a periodic potential. Based on the tight-binding model, we study graphene under a one-dimensional (1D) modulated magnetic field which contains both a uniform and a staggered component. New chiral current-carrying edge states are generated at the interfaces where the staggered component changes direction. These edge states lead to an unusual integer quantum Hall effect (QHE) in graphene, which can be observed experimentally by a standard four-terminal Hall measurement. When Zeeman spin splitting is considered, a novel state is predicted where the electron edge currents with opposite polarization propagate in the opposite directions at one sample boundary, whereas propagate in the same directions at the other sample boundary.Comment: 5 pages, 4 figure

    Single hole motion in LaMnO3_3

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    We study single hole motion in LaMnO3_3 using the classical approximation for JT lattice distortions, a modified Lang-Firsov approximation for dynamical breathing-mode phonons, and the self-consistent Born approximation (verified by exact diagonalization) for hole-orbital-excitation scattering. We show that in the realistic parameter space for LaMnO3_3, quantum effects of electron-phonon interaction are small. The quasiparticle bandwidth W2.2JW \simeq 2.2J in the purely orbital t-J model. It is strikingly broadened to be of order tt by strong static Jahn-Teller lattice distortions even when the polaronic band narrowing is taken into account.Comment: 4 pages, 4 eps figure

    Tuning Kinetic Magnetism of Strongly Correlated Electrons via Staggered Flux

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    We explore the kinetic magnetism of the infinite-UU repulsive Hubbard models at low hole densities on various lattices with nearest-neighbor hopping integrals modulated by a staggered magnetic flux ±ϕ\pm\phi. Tuning ϕ\phi from 0 to π\pi makes the ground state (GS) change from a Nagaoka-type ferromagnetic state to a Haerter-Shastry-type antiferromagnetic state at a critical ϕc\phi_c, with both states being of kinetic origin. Intra-plaquette spin correlation, as well as the GS energy, signals such a quantum criticality. This tunable kinetic magnetism is generic, and appears in chains, ladders and two-dimensional lattices with squares or triangles as elementary constituents.Comment: 4 pages, 5 figures, 1 tabl