20,009 research outputs found
Topological-Fermi-Liquid to Quantum-Hall-Liquid Transitions: -Band and -Band Fermions in a Magnetic Field
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 -band
spinless fermionic system realizable with ultracold atoms in optical lattice,
and a -band spinful fermionic system closely related to giant orbital Hall
effects in transition metals and their compounds.Comment: 4 pages, 4 figure
Tuning Kinetic Magnetism of Strongly Correlated Electrons via Staggered Flux
We explore the kinetic magnetism of the infinite- repulsive Hubbard models
at low hole densities on various lattices with nearest-neighbor hopping
integrals modulated by a staggered magnetic flux . Tuning from
0 to makes the ground state (GS) change from a Nagaoka-type ferromagnetic
state to a Haerter-Shastry-type antiferromagnetic state at a critical ,
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
Extended staggered-flux phases in two-dimensional lattices
Based on the so called - model in two-dimensional (2D) lattices, we
investigate the stabilities of a class of extended staggered-flux (SF) phases
(which are the extensions of the SF phase to
generalized spatial periods) against the Fermi-liquid phase. Surprisingly, when
away from the nesting electron filling, some extended-SF phases take over the
dominant SF phase (the SF phase for the square
lattice, a SF phase for the triangular one), compete with the
Fermi-liquid phase in nontrivial patterns, and still occupy significant space
in the phase diagram through the advantage in the total electronic kinetic
energies. The results can be termed as the generalized Perierls
orbital-antiferromagnetic instabilities of the Fermi-liquid phase in 2D
lattice-electron models.Comment: 5 pages, 5 figure
Maximum Estrada Index of Bicyclic Graphs
Let be a simple graph of order , let
be the eigenvalues of the
adjacency matrix of . The Esrada index of is defined as
. In this paper we determine the unique
graph with maximum Estrada index among bicyclic graphs with fixed order
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