An-harmonic Oscillations and Superconductivity in (Cu0.5-xKxTl0.5)Ba2Ca2Cu3-y-z ZnyCdzO10-delta (x=0, 0.25; y = z=0, 0.25, 0.5, 0.75, 1) Samples

摘要

(Cu0.5-xKxTl0.5)Ba2Ca2Cu3-y-z ZnyCdzO10-delta (x = 0, 0.25; y = z = 0, 0.25, 0.5, 0.75, 1) samples are synthesized for the investigation of role of an-harmonic oscillations in the mechanism of high T-c superconductivity. In the conducting planes, the carrier density is enhanced by K doping at the charge reservoir layer (Cu0.5Tl0.5)Ba2O4-delta by synthesizing (Cu0.25K0.25Tl0.5)Ba2Ca2Cu3-y-zZnyCdzO10-delta (y = z = 0, 0.25, 0.5, 0.75, 1) samples. The (Cu0.5-xKxTl0.5)Ba2Ca2Cu3-y-z ZnyCdzO10-delta (x = 0, 0.25; y = z = 0, 0.25, 0.5, 0.75, 1) samples were prepared by employing two-step solid-state reaction method accomplished at 860 degrees C and understand their superconducting properties by resistivity measurements, X-ray diffraction analysis, and FTIR absorption measurements. The orthorhombic unit cell of our samples was confirmed via XRD analysis. The analysis also reflected the increase in c-axis length and the volume of the unit cell with the enhanced dopants (Cd and Zn) concentration. The suppression of T-c(onset) and T-c(R = 0) was found with the increasing concentration of Zn and Cd. An improvement in the T-c(onset) observed in samples doped by K that arises due to increase in the density of free carriers supplied by alkali atoms. With the increasing content of Cd and Zn, the unit cell exhibits the softening of Cu(1)-O-A-Cu(2) and Tl-O-A-Cu(2) apical oxygen mode and hardening of planar oxygen mode. From FIC analysis, the T-c(mf) and T* and various cross over temperature were shifted towards lower temperature with the enhanced Zn and Cd dopant concentration. The value of alpha determining the defect density also increases with the increasing dopant (Zn and Cd) concentration. The numerical values of different parameter like B-c0(T), B-c1(T), J(c)(0), and E-break showing increasing trend but the phase relaxation time of the carriers tau(phi) points out decreasing trend with the enhanced doping of Cd and Zn. Moreover, these parameters reflected inferior values in K-doped samples relative to K-undoped samples. The value of other parameter like coherence length xi(c(0)) along c-axis, interlayer coupling J, magnetic field penetration depth lambda(p.d), the Ginzburg Landau (GL) parameter kappa, and the Fermi velocity V-F of the carriers decreases as doping of Zn and Cd enhanced. These parameters show superior values in K-doped samples relative to K-undoped samples due to increase in the density of free carriers supplied by K atoms. The negative values of real part of dielectric constant suppress in both K undoped and K doped samples with increasing concentration of Cd and Zn. The imaginary part of dielectric constant and ac conductivity showing suppression in their negative values in K undoped samples while showing increase in absolute values in K doped samples with increasing concentration of Cd and Zn.