1,378 research outputs found
Electron spectral functions in a quantum dimer model for topological metals
We study single electron spectral functions in a quantum dimer model
introduced by Punk, Allais and Sachdev (Ref. [1]). The Hilbert space of this
model is spanned by hard-core coverings of the square lattice with two types of
dimers: ordinary bosonic spin-singlets, as well as fermionic dimers carrying
charge +e and spin 1/2, which can be viewed as bound-states of spinons and
holons in a doped resonating valence bond (RVB) liquid. This model realizes a
metallic phase with topological order and captures several properties of the
pseudogap phase in hole-doped cuprates, such as a reconstructed Fermi surface
with small hole-pockets and a highly anisotropic quasiparticle residue in the
absence of any broken symmetries. Using a combination of exact diagonalization
and analytical methods we compute electron spectral functions and show that
this model indeed exhibits a sizeable antinodal pseudogap, with a momentum
dependence deviating from a simple d-wave form, in accordance with experiments
on underdoped cuprates.Comment: 13 pages, 7 figure
Topological Transitions for Lattice Bosons in a Magnetic Field
We study the Hall response of the Bose-Hubbard model subjected to a magnetic
field. We show that the Hall conductivity is proportional to the particle
density plus an integer. The phase diagram is intersected by topological
transitions between different integer values. These transitions originate from
points in the phase diagram with effective charge conjugation symmetry, and are
attributed to degeneracies in the many body spectrum which serve as sources for
the Berry curvature. We find that extensive regions in the phase diagram
exhibit a negative Hall conductivity, implying that flux flow is reversed in
these regions - vortices there flow upstream. We discuss experimental
implications of our findings.Comment: 11 pages, 7 figure
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