Seminário de Matéria Condensada - 07/06/2018, 11:00, Sala 426 (Torre Nova)

Correlations among charge order, superconducting interaction, Tc and superfluid density in cuprate superconductors

Evandro Vidor de Mello (UFF)

After more than 30 years the problem of high-Tc superconductor is still open. A revealing experiment was the scaling between superfluid density $\rho_{sc}$ and Tc established long ago. The values of $\rho_sc$ are orders of magnitude lower than conventional superconductors, implying that phase fluctuations are important. Another universal feature is the presence of an incommensurate charge order (CO) with $\lambda_{CO}$ wavelength smaller than the superconducting coherence length $\xi$. We simulate CO patterns with a Ginzburg-Landau free energy with $\lambda_{CO}$ modulations. The charge fluctuations yield the superconducting interaction that leads to the amplitudes $\Delta_d({\bf r})$ in the grains. The intergrain Josephson coupling $E_J \propto \rho_{\rm sc}$ establishes long range phase order and is used to derive the $\rho_{sc}(0)-T_c$ for four cuprate families. Through $E_J$ and the resistivity we can infer the real superconducting gap. The method works also with very small charge variations and reproduces the new $\rho_{sc}(0)-T_c$ linear relation on overdoped La$_{2-x}$Sr$_x$CuO$_4$ films, providing a unified approach to under and overdoped cuprates.

 
 
evendro-mello2018.txt · Last modified: 2018/06/03 18:12 by caio
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