Phenomenological Ginzburg-Landau-like theory for superconductivity in the cuprates - Condensed Matter > SuperconductivityReportar como inadecuado

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Abstract: We propose a phenomenological Ginzburg-Landau-like theory of cupratesuperconductivity. The free energy is expressed as a functional F of thespin-singlet pair amplitude psi ij=psi m=Delta m expi phi m; i and j arenearest-neighbor sites of the Cu lattice in which the superconductivity isbelieved to primarily reside and m labels the site at the center of the bondbetween i and j. The system is modeled as a weakly coupled stack of suchplanes. We hypothesize a simple form, FDelta,phi=sum m A Delta m^2+ BDelta m^4-2+C sum Delta m Delta n cosphi m-phi n, for the functional.The coefficients A, B and C are determined from comparison with experiments. Wework out a number of consequences of the proposed functional for specificchoices of A, B and C as functions of hole density x and temperature T. Therecan be a rapid crossover of from small to large values as A changessign on lowering T and the crossover temperatures is identified with theobserved pseudogap temperature. The superconducting phase-coherence transitionoccurs at a different temperature T c, and describes superconductivity withd-wave symmetry for C>0. We calculate T cx which has the observed parabolicshape, being strongly influenced by the coupling between Delta m and phi mpresent in F. The superfluid density, the local gap magnitude, the specificheat with and without a magnetic field and vortex properties are obtainedusing F. We compare our results successfully with experiments. We also obtainthe electron spectral density as influenced by the coupling between theelectrons and the pair correlation function calculated from F. Features such astemperature dependent Fermi arcs, antinodal pseudogap filling temperature,pseudogapped density of states in different momentum regions of the Fermisurface and `bending- of the energy gap versus momentum on the Fermi surfaceemerge from the theory.

Autor: Sumilan Banerjee, T. V. Ramakrishnan, Chandan Dasgupta


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