<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">c</mml:mi></mml:math>Axis Superfluid Response of Copper Oxide Superconductors

Abstract

A novel interplay between $d$-wave superconducting order parameter symmetry and the underlying Cu $3d$ orbital based electronic structure of copper oxides leads to a striking anisotropy in the superfluid response of these systems. In clean tetragonal materials the $c$ axis penetration depth increases as ${T}^{5}$ at low temperature, in contrast to linear $T$ behavior in the $\mathrm{ab}$ plane. Disorder is a relevant perturbation which causes all components of the superfluid response to depend quadratically on temperature at low temperature. However, the crossover temperature scale from the intrinsic $d$-wave behavior to the disorder dominated behavior for the in-plane response may be different from that for the out-plane response.