2,386 research outputs found
Band structure renormalization and weak pseudogap behavior in Na_{0.33}CoO_2: Fluctuation exchange study based on a single band model
Based on a single band Hubbard model and the fluctuation exchange
approximation, the effective mass and the energy band renormalization in
NaCoO is elaborated. The renormalization is observed to exhibit
certain kind of anisotropy, which agrees qualitatively with the angle-resolved
photoemission spectroscopy (ARPES) measurements. Moreover, the spectral
function and density of states (DOS) in the normal state are calculated, with a
weak pseudogap behavior being seen, which is explained as a result of the
strong Coulomb correlations. Our results suggest that the large Fermi surface
(FS) associated with the band plays likely a central role in the
charge dynamics.Comment: 5 pages, 5 figure
Mottness induced phase decoherence suggests Bose-Einstein condensation in overdoped cuprate high-temperature superconductors
Recent observations of diminishing superfluid phase stiffness in overdoped
cuprate high-temperature superconductors challenges the conventional picture of
superconductivity. Here, through analytic estimation and verified via
variational Monte Carlo calculation of an emergent Bose liquid, we point out
that Mottness of the underlying doped holes dictates a strong phase fluctuation
of the superfluid at moderate carrier density. This effect turns the expected
doping-increased phase stiffness into a dome shape, in good agreement with the
recent observation. Specifically, the effective mass divergence due to
"jamming" of the low-energy bosons reproduces the observed nonlinear relation
between phase stiffness and transition temperature. Our results suggest a new
paradigm, in which the high-temperature superconductivity in the cuprates is
dominated by physics of Bose-Einstein condensation, as opposed to
pairing-strength limited Cooper pairing.Comment: 6+3 pages, 4+1 figure
Orbital-transverse density-wave instabilities in iron-based superconductors
Besides the conventional spin-density-wave (SDW) state, a new kind of
orbital-transverse density-wave (OTDW) state is shown to exist generally in
multi-orbital systems. We demonstrate that the orbital character of Fermi
surface nesting plays an important role in density responses. The relationship
between antiferromagnetism and structural phase transition in LaFeAsO (1111)
and BaFeAs (122) compounds of iron-based superconductors may be
understood in terms of the interplay between the SDW and OTDW with a
five-orbital Hamiltonian. We propose that the essential difference between 1111
and 122 compounds is crucially determined by the presence of the
two-dimensional -like Fermi surface around (0,0) being only in 1111
parent compounds.Comment: several parts were rewritten for clarity. 6 pages, 3 figures, 1 tabl
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