Probing pairing symmetry of Sm 1.85Ce 0.15CuO 4 via highly-sensitive voltage measurements: Evidence for strong impurity scattering

• Published in: Physics letters. A Vol. 359; no. 6; pp. 696 - 699
• Main Authors: Lanfredi, A.J.C., Sergeenkov, S., Araujo-Moreira, F.M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2006
• Subjects: Electron-doped superconductors; Pairing symmetry; Penetration depth; 74.78.Bz; 74.20.Rp; 74.70.-b; Electron-doped superconductors; Pairing symmetry; Penetration depth
• ISSN: 0375-9601; 1873-2429
• DOI: 10.1016/j.physleta.2006.07.010

Using a highly-sensitive home-made mutual-inductance technique, temperature profiles of the magnetic penetration depth λ ( T ) in the optimally-doped Sm 1.85Ce 0.15CuO 4 thin films have been extracted. The low-temperature behavior of λ ( T ) is found to be best-fitted by linear Δ λ ( T ) / λ ( 0 ) = ln ( 2 ) k B T / Δ 0 and quadratic Δ λ ( T ) / λ ( 0 ) = Γ − 1 / 2 Δ 0 − 3 / 2 T 2 laws above and below T = 0.22 T C , respectively, which clearly indicates the presence of d-wave pairing mechanism dominated by strong paramagnetic scattering at the lowest temperatures. The best fits produce Δ 0 / k B T C = 2.07 and Γ / T C = 0.25 ( T C / Δ 0 ) 3 for the estimates of the nodal gap parameter and impurity scattering rate.