591 research outputs found
Finite-Energy Landau Liquid Theory for the 1D Hubbard Model: Pseudoparticle Energy Bands and Degree of Localization/Delocalization
This paper is part of a broader study whose main goal is the study of the
finite-energy spectral properties of the non-perturbative one-dimensional (1D)
Hubbard model and the evaluation of finite-energy correlation-function
expressions. Here we study the deviations from the ground state values of
double occupancy which result from creation or annihilation of holons, spinons,
and pseudoparticles. The band-momentum dependence of the obtained
double-occupancy spectra provides important information on the degree of
localization/delocalization of the real-space lattice electron site
distribution configurations associated with the pseudoparticles. We also study
the band-momentum, on-site electronic repulsion, and electronic density
dependence of the pseudoparticle energy bands. The shape of these bands plays
an important role in the finite-energy spectral properties of the model. Such a
shape defines the form of the lines in the momentum-energy/frequency plane
where the peaks and edges of the one-electron and two-electron spectral weight
of physical operators are located. Our findings are useful for the study of the
one-electron and two-electron spectral weight distribution of physical
operators.Comment: 24 pages, 9 figures. Accepted for publication in Physical Review
Effects of disorder on the vortex charge
We study the influence of disorder on the vortex charge, both due to random
pinning of the vortices and due to scattering off non-magnetic impurities. In
the case when there are no impurities present, but the vortices are randomly
distributed, the effect is very small, except when two or more vortices are
close by. When impurities are present, they have a noticeable effect on the
vortex charge. This, together with the effect of temperature, changes
appreciably the vortex charge. In the case of an attractive impurity potential
the sign of the charge naturally changes.Comment: 10 pages, 16 figures. Accepted in Phys. Rev.
Emergent Nesting of the Fermi Surface from Local-Moment Description of Iron-Pnictide High-Tc Superconductors
We uncover the low-energy spectrum of a t-J model for electrons on a square
lattice of spin-1 iron atoms with 3dxz and 3dyz orbital character by applying
Schwinger-boson-slave-fermion mean-field theory and by exact diagonalization of
one hole roaming over a 4 x 4 x 2 lattice. Hopping matrix elements are set to
produce hole bands centered at zero two-dimensional (2D) momentum in the
free-electron limit. Holes can propagate coherently in the t-J model below a
threshold Hund coupling when long-range antiferromagnetic order across the d+ =
3d(x+iy)z and d- = 3d(x-iy)z orbitals is established by magnetic frustration
that is off-diagonal in the orbital indices. This leads to two hole-pocket
Fermi surfaces centered at zero 2D momentum. Proximity to a commensurate
spin-density wave (cSDW) that exists above the threshold Hund coupling results
in emergent Fermi surface pockets about cSDW momenta at a quantum critical
point (QCP). This motivates the introduction of a new Gutzwiller wavefunction
for a cSDW metal state. Study of the spin-fluctuation spectrum at cSDW momenta
indicates that the dispersion of the nested band of one-particle states that
emerges is electron-type. Increasing Hund coupling past the QCP can push the
hole-pocket Fermi surfaces centered at zero 2D momentum below the Fermi energy
level, in agreement with recent determinations of the electronic structure of
mono-layer iron-selenide superconductors.Comment: 41 pages, 12 figures, published versio
Local density of states of a strongly type-II d-wave superconductor: The binary alloy model in a magnetic field
We calculate self-consistently the local density of states (LDOS) of a d-wave
superconductor considering the scattering of the quasiparticles off randomly
distributed impurities and off externally induced vortices. The impurities and
the vortices are randomly distributed but the vortices are preferably located
near the impurities. The increase of either the impurity repulsive potential or
the mpurity density only affects the density of states (DOS) slightly. The
dominant effect is due to the vortex scattering. The results for the LDOS agree
qualitatively with experimental results considering that most vortices are
pinned at the impurities.Comment: To be published in Physical Review
Hall conductance of a pinned vortex lattice in a high magnetic field
We calculate the quasiparticle contribution to the zero temperature Hall
conductance of two-dimensional extreme type-II superconductors in a high
magnetic field, using the Landau basis. As one enters the superconducting phase
the Hall conductance is renormalized to smaller values, with respect to the
normal state result, until a quantum level-crossing transition is reached. At
high values of the order parameter, where the quasiparticles are bound to the
vortex cores, the Hall conductance is expected to tend to zero due to a theorem
of Thouless.Comment: To appear in Journ. Phys. : Cond. Matte
- …