On the characteristic lengths of the high T_c oxide superconductors

Abstract

We discuss the fundamental characteristic lengths, namely ζ₀ the zero temperature coherence length, Λ_L the London penetration depth, and l the carrier mean free path, for the oxide high T_c superconductors in relation to the latest experimental measurements. We examine theoretically why ζ₀ is so small and argue that its smallness is independent of the nature of the pairing mechanism of superconductivity. We also compare various measurements from the point of view of Pippard's theory for both the normal and the superconducting states respectively. Several questions are posed by these interpretations of the experimental data.

Key Words:

• High T_c superconductors
• Coherence length
• Penetration depth
• Mean free path