Infrared signature of the superconducting state in Pr2-xCexCuO4 -: art. no. 132502

We measured the far infrared reflectivity of two superconducting Pr2-xCexCuO4 films above and below T-c. 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 T-c as 2Delta(max)/k(B)T(c)approximate to4.7. We determined absolute values of the penetration depth at 5 K as lambda(ab)=(3300+/-700) Angstrom for x=0.15 and lambda(ab)=(2000+/-300) Angstrom for x=0.17. A spectral weight analysis shows that the Ferrell-Glover-Tinkham sum rule is satisfied at conventional low energy scales similar to4Delta(max).