Two-Gap Superconductivity in the Cuprate Superconductor La1.83Sr0.17CuO4

Abstract

Based on the idea of K.A. Muller [Nature (London) 377, 133 (1995)] that two superconducting condensates with s-wave and d-wave symmetries are present in high-temperature cuprate superconductors, we performed measurements of the in-plane magnetic field penetration depth (λ ab) in single-crystal La1.83Sr0.17CuO4 by means of the muon-spin rotation technique. The temperature dependence of λ −2 ab has an inflection point around 10–15 K, suggesting the opening of two superconducting gaps: a large gap (Δ1 d ) with a d-wave and a small gap (Δ2 s ) with an s-wave symmetry. The zero-temperature values of the gaps at μ 0 H =, obtained from the global fit of muon data, were found to be Δ1 d (0) = 8.2(1) meV and Δ2 s (0) = meV. With increasing magnetic field the contribution of Δ2 s decreases substantially, in contrast to an almost constant contribution of Δ d 1. The magnetic field dependence of the transition temperature T c and the distribution of the local magnetic fields P(B) in La1.83Sr0.17CuO4 superconductor in the mixed state were also found to be consistent with the presence of two superconducting gaps.