Kondo ss-dd exchange interaction in the CuO2_2 plane as the long sought mechanism of high temperature superconductivity in cuprates

The well-known Pavarini et al. [Phys. Rev. Lett. 87, 047003 (2001)] correlation between the critical temperature $T_c$, max and the shape of the Fermi contour of the optimally hole-doped cuprates are explained within the framework of the BCS theory with Kondo exchange interaction incorporated as a pairing mechanism. The strong influence of the relative position of the Cu4$s$ level with respect to the Cu3$d_{x^2-y^2}$ level on the critical temperature $T_c$ reveals why the $s$-$d$ hybridization of the conduction band is so important. This hybridization is proportional to the $s$-$d$ exchange scattering amplitude between the conduction electrons -- the mechanism of d-wave pairing in the CuO$_2$ plane. In other words the Kondo interaction considered as a pairing mechanism in the CuO$_2$ plane gives a natural explanation of the correlation between the critical temperature and the shape of the Fermi contour. The lack of an alternative explanation for the description of the critical temperature of optimally doped cuprates for several decades gives a hint that the long sought pairing mechanism has already been found.Comment: 9 pages, 3 figures, 2 tables, 43 ref

Possible zero sound in layered perovskites with ferromagnetic ss-dd exchange interaction

We analyze the conditions for observation of zero sound in layered perovskites with transition metal ion on chalcogenide oxidizer. We conclude that propagation of zero sound is possible only for anti-ferromagnetic sign of the $s$-$d$ interaction. If the $s$-$d$ exchange integral $J_{sd}$ has antiferromagnetic sign, as it is perhaps in the case for layered cuprates, zero sound is a thermally activated dissipation mode,which generates only "hot spots" in the Angle Resolved Photoemission Spectroscopy (ARPES) data along the Fermi contour. We predict that zero sound will be observable for transition metal perovskites with 4$s$ and 3$d$ levels close to the $p$-level of the chalcogenide. The simultaneous lack of superconductivity, the appearance of hot spots in ARPES data, and the proximity of the three named levels, represents the significant hint for the choice of material to be investigated.Comment: 7 pages, 4 figures, 30 reference

Hot spots along the Fermi contour of high-TcT_c cuprates analyzed by ss-dd exchange interaction

We perform a thorough theoretical study of the electron properties of a generic CuO$_2$ plane in the framework of Shubin-Kondo-Zener $s$-$d$ exchange interaction that simultaneously describes the correlation between $T_c$ and the Cu4$s$ energy. To this end, we apply the Pokrovsky theory [J. Exp. Theor. Phys. 13, 447-450 (1961)] for anisotropic gap BCS superconductors. It takes into account the thermodynamic fluctuations of the electric field in the dielectric direction perpendicular to the conducting layers. We microscopically derive a multiplicatively separable kernel able to describe the scattering rate in the momentum space, as well as the superconducting gap anisotropy within the BCS theory. These findings may be traced back to the fact that both the Fermi liquid and the BCS reductions lead to one and the same reduced Hamiltonian involving a separable interaction, such that a strong electron scattering corresponds to a strong superconducting gap and vice versa. Moreover, the superconducting gap and the scattering rate vanish simultaneously along the diagonals of the Brillouin zone. We would like to stress that our theoretical study reproduces the phenomenological analysis of other authors aiming at describing Angle Resolved Photoemission Spectroscopy measurements. Within standard approximations one and the same $s$-$d$ exchange Hamiltonian describes gap anisotropy of the superconducting phase and the anisotropy of scattering rate of charge carriers in the normal phase.Comment: 10 pages, 3 figures, 56 reference

Electric Oscillations Generated by Fluctuation Cooper Pairs

A short review of the history and the contemporary numerical calculations of the operation of an electronic device for generation of electric oscillations by negative differential conductivity of a supercooled below the critical temperature superconductor. The superconductor is cooled below the critical temperature at applied small constant electric field, which keeps the superconductor in normal state. To simulate the device operation, beforehand analytical expressions for the conductivity of nano-structured superconductors supercooled below the critical temperature in electric field are used. The numerical analysis meant to alleviate the development of a device shows that the region of negative differential conductivity of the current voltage characteristics leads to generation of electric oscillations. The study of layered high temperature superconductors and radiated electromagnetic waves in space will be an important problem of the future space technology.Comment: Master degree thesis of Aleksander Petkov with scientific advisor Albert Varonov and consultant Todor Mishonov, 20 pages, 16 figures, 1 table; version 2 has the master thesis added to the source files (filename "MasterThesis.pdf", Bulgarian translation