Infrared Signature of the Superconducting State in Pr(2-x)Ce(x)CuO(4)

TL;DR

This study investigates the infrared optical properties of Pr(2-x)Ce(x)CuO(4) superconductors, revealing an anisotropic gap and providing measurements of the penetration depth and spectral weight redistribution below Tc.

Contribution

First direct infrared measurements of the superconducting gap and penetration depth in Pr(2-x)Ce(x)CuO(4), confirming anisotropic gap features and sum rule satisfaction.

Findings

Superconducting gap scales with Tc as 2 Delta / kB Tc ~ 4.7.

Penetration depth at 5 K is approximately 3300 Å for x=0.15.

Spectral weight analysis confirms sum rule at ~4 Delta_{max}.

Abstract

We measured the far infrared reflectivity of two superconducting Pr(2-x)Ce(x)CuO(4) films above and below Tc. The reflectivity in the superconducting state increases and the optical conductivity drops at low energies, in agreement with the opening of a (possibly) anisotropic superconducting gap. The maximum energy of the gap scales roughly with Tc as 2 Delta_{max} / kB Tc ~ 4.7. We determined absolute values of the penetration depth at 5 K as lambda_{ab} = (3300 +/- 700) A for x = 0.15 and lambda_{ab} = (2000 +/- 300) A for x = 0.17. A spectral weight analysis shows that the Ferrell-Glover-Tinkham sum rule is satisfied at conventional low energy scales \~ 4 Delta_{max}.