3 research outputs found
Spectral signatures of modulated d-wave superconducting phases
We calculate within a mean-field theory the spectral signatures of various
striped d-wave superconducting phases. We consider both in-phase and anti-phase
modulations of the superconducting order across a stripe boundary, and the
effects of coexisting inhomogeneous orders, including spin stripes, charge
stripes, and modulated d-density-wave. We find that the anti-phase modulated
d-wave superconductor exhibits zero-energy spectral weight, primarily along
extended arcs in momentum space. Concomitantly, a Fermi surface appears and
typically includes both open segments and closed pockets. When weak homogeneous
superconductivity is also present the Fermi surface collapses onto nodal
points. Among them are the nodal points of the homogeneous d-wave
superconductor, but others typically exist at positions which depend on the
details of the modulation and the band structure. Upon increasing the amplitude
of the constant component these additional points move towards the edges of the
reduced Brillouin zone where they eventually disappear. The above signatures
are also manifested in the density of states of the clean, and the disordered
system. While the presence of coexisting orders changes some details of the
spectral function, we find that the evolution of the Fermi-surface and the
distribution of the low-energy spectral weight are largely unaffected by them.Comment: Published version. We added an appendix including the detailed
Hamiltonians, and made other minor change
Weak-coupling phase diagrams of bond-aligned and diagonal doped Hubbard ladders
We study, using a perturbative renormalization group technique, the phase
diagrams of bond-aligned and diagonal Hubbard ladders defined as sections of a
square lattice with nearest-neighbor and next-nearest-neighbor hopping. We find
that for not too large hole doping and small next-nearest-neighbor hopping the
bond-aligned systems exhibit a fully spin-gapped phase while the diagonal
systems remain gapless. Increasing the next-nearest-neighbor hopping typically
leads to a decrease of the gap in the bond-aligned ladders, and to a transition
into a gapped phase in the diagonal ladders. Embedding the ladders in an
antiferromagnetic environment can lead to a reduction in the extent of the
gapped phases. These findings suggest a relation between the orientation of
hole-rich stripes and superconductivity as observed in LSCO.Comment: Published version. The set of RG equations in the presence of
magnetization was corrected and two figures were replace