Seminar on Disorder and strong electron correlations: "Ginzburg Landau like theory of high temperature superconductivity in the cuprates"
Tiruppattur V. RAMAKRISHNAN
(Banaras Hindu University, Varanasi & Indian Institute of Science, Bangalore )
I describe here a new approach to high temperature superconductivity in the cuprates. The free energy of the system is described as a function of the (Cooper pair bond) order parameter, in the spirit of the original phenomenological Ginzburg Landau theory; our functional is superficially identical with its well known simple form. We use it to compare our results successfully with a wide range of observations on cuprates as a function of hole doping x and temperature T. We obtain the pseudogap curve, the superconducting transition temperature Tc, the superfluid density, the specific heat (with and without a magnetic field) all in the (x,T) plane, and the zero temperature vortex structure. We also find, within our picture, the coupling of electrons to pair degrees of freedom, and use this to explore the spectral function as influenced by inevitable superconducting pair fluctuations for electronic energies near the Fermi energy. The results are confronted with recent high resolution ARPES measurements, eg Fermi arcs above Tc, the development of the pseudogap in the antinodal region, and the 'bending' of the gap below Tc as a function of the angular location on the Fermi surface. The work reported here was done in collaboration with Sumilan Banerjee and Chandan Dasgupta of the IISc, Bangalore. If time permits, speculations on microscopics and on quantum oscillations will be mentioned.
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