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We report on an infrared study of carrier dynamics within the CuO$_{2}$ planes in heavily underdoped detwinned single crystals of YBa$_{2}$Cu$_{3}$O$% _{y}$. In an effort to reveal the electronic structure near the onset of superconductivity, we investigate the strong anisotropy of the electromagnetic response due to an enhancement of the scattering rate along the a-axis. We propose that the origin of this anisotropy is related to a modulation of the electron density within the CuO$_{2}$ planes.
We use inelastic neutron scattering to study the temperature dependence of the spin excitations of a detwinned superconducting YBa$_2$Cu$_3$O$_{6.45}$ ($T_c=48$ K). In contrast to earlier work on YBa$_2$Cu$_3$O$_{6.5}$ ($T_c=58$ K), where the promine
We report the magnetic field-amplitude and field-angle dependence of the superconducting onset temperature Tc_onset of the organic superconductor (TMTSF)2ClO4 in magnetic fields H accurately aligned to the conductive ab plane. We revealed that the ra
Short-range lattice superstructures have been studied with high-energy x-ray diffuse scattering in underdoped, optimally doped, and overdoped $rm (Y,Ca)Ba_2 Cu_3 O_{6+x}$. A new four-unit-cell superstructure was observed in compounds with $xsim 0.95$
The far-infrared dielectric response of superlattices (SL) composed of superconducting YBa$_{2}$Cu$_{3}$O$_{7}$ (YBCO) and ferromagnetic La$_{0.67}$% Ca$_{0.33}$MnO$_{3}$ (LCMO) has been investigated by ellipsometry. A drastic decrease of the free ca
We have synthesized polycrystalline samples and single crystals of Fe(Te1-xSx)y, and characterized their properties. Our results show that the solid solution of S in this system is limited, < 30%. We observed superconductivity at ~ 9 K in both polycr