284 research outputs found
Coexistence of superconductivity and antiferromagnetism in self-doped bilayer t-t'-J model
A self-doped bilayer t-t'-J model of an electron- and a hole-doped planes is
studied by the slave-boson mean-field theory. A hopping integral between the
differently doped planes, which are generated by a site potential, are
renormalized by the electron-electron correlation. We find coexistent phases of
antiferromagnetic (AFM) and superconducting orders, although the magnitudes of
order parameters become more dissimilar in the bilayer away from half-filling.
Fermi surfaces (FS's) with the AFM order show two pockets around the nodal and
the anti-nodal regions. These results look like a composite of electron- and
hole-doped FS's. In the nodal direction, the FS splitting is absent even in the
bilayer system, since one band is flat due to the AFM order.Comment: 6 pages, 4 figure
Effect of Co doping on the in-plane anisotropy in the optical spectrum of underdoped Ba(Fe1-xCox)2As2
We investigated the anisotropy in the in-plane optical spectra of detwinned
Ba(Fe1-xCox)2As2. The optical conductivity spectrum of BaFe2As2 shows
appreciable anisotropy in the magnetostructural ordered phase, whereas the dc
resistivity is almost isotropic at low temperatures. Upon Co doping, the
resistivity becomes highly anisotropic, while the finite-energy intrinsic
anisotropy is suppressed. It is found that anisotropy in resistivity arises
from anisotropic impurity scattering from doped Co atoms, extrinsic in origin.
Intensity of a specific optical phonon mode is also found to show striking
anisotropy in the ordered phase. The anisotropy induced by Co impurity and that
observed in the optical phonon mode are hallmarks of the highly polarizable
electronic state in the ordered phase.Comment: 5 pages, 4 figure
Microwave Penetration Depth and Quasiparticle Conductivity in PrFeAsO_1-y Single Crystals : Evidence for a Full-Gap Superconductor
In-plane microwave penetration depth and quaiparticle
conductivity at 28 GHz are measured in underdoped single crystals of the
Fe-based superconductor PrFeAsO ( K) by using a
sensitive superconducting cavity resonator. shows flat
dependence at low temperatures, which is incompatible with the presence of
nodes in the superconducting gap . The temperature dependence
of the superfluid density demonstrates that the gap is non-zero
() all over the Fermi surface. The microwave
conductivity below exhibits an enhancement larger than the coherence
peak, reminiscent of high- cuprate superconductors.Comment: 4 pages, 3 figures. Version accepted for publication in Phys. Rev.
Lett. For related results of hole-doped 122 system, see arXiv:0810.350
Uniform Mixing of High-Tc Superconductivity and Antiferromagnetism on a Single CuO2 Plane in Hg-based Five-layered Cuprate
We report a site selective Cu-NMR study on under-doped Hg-based five-layered
high- cuprate HgBa2Ca4Cu5Oy with a Tc=72 K. Antiferromagnetism (AF)
has been found to take place at TN=290 K, exhibiting a large antiferromagnetic
moment of 0.67-0.69uB at three inner planes (IP's). This value is comparable to
the values reported for non-doped cuprates, suggesting that the IP may be in a
nearly non-doped regime. Most surprisingly, the AF order is also detected with
M(OP)=0.1uB even at two outer planes (OP's) that are responsible for the onset
of superconductivity (SC). The high-Tc SC at Tc = 72 K can uniformly coexist on
a microscopic level with the AF at OP's. This is the first microscopic evidence
for the uniform mixed phase of AF and SC on a single CuO2 plane in a simple
environment without any vortex lattice and/or stripe order.Comment: 4 pages, 4 figures. To be published in Phys.Rev.Let
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