Suppression of the s-Wave Order Parameter Near the Surface of the Infinite-Layer Electron-Doped Cuprate Superconductor Sr0.9La0.1CuO2

Abstract

The temperature dependencies of the in-plane (λab) and out-of-plane (λc) components of the magnetic field penetration depth were investigated near the surface and in the bulk of the electron-doped superconductor Sr0.9La0.1CuO2 by means of magnetization measurements. The measured λab(T) and λc(T) were analyzed in terms of a two-gap model with mixed s+d-wave symmetry of the order parameter. λab(T) is well described by an almost pure anisotropic d-wave symmetry component (≃96%), mainly reflecting the surface properties of the sample. In contrast, λc(T) exhibits a mixed s+d-wave order parameter with a substantial s-wave component of more than 50%. The comparison of λab−2(T) measured near the surface with that determined in the bulk by means of the muon-spin rotation/relaxation technique demonstrates that the suppression of the s-wave component of the order parameter near the surface is associated with a reduction of the superfluid density by more than a factor of two.

Superconductivity and the Jahn–Teller Polaron

“…Müller [26,27] proposed that the order parameter has a mixed s + d symmetry, changing from a dominant d-wave character near the surface to a more swave character in the bulk of the superconductor. This scenario of coexisting s + d order parameters is clearly supported by recent AC magnetization and µSR studies of the inplane (λ ab ) and out-of-plane (λ c ) magnetic field penetration depths near the surface and in the bulk of the electron-doped cuprate superconductor Sr 0.9 La 0.1 CuO 2 [28].…”

From SrTiO3 to Cuprates and Back to SrTiO3: A Way Along Alex Müller’s Scientific Career

“…Müller [69]. For more details of this study, we refer to the contribution of Khasanov et al in Reference [71].…”

“…Müller, to conclude that the gap symmetry may change from purely d-wave near the surface to more s-wave, like in the bulk of the superconductor [69,70]. We investigated the temperature dependencies of the in-plane (λ ab ) and out-of-plane (λ c ) magnetic field penetration depths near the surface and in the bulk of the electron-doped superconductor Sr 0.9 La 0.1 CuO 2 by means of AC magnetization and µSR measurements [71]. These studies provide evidence that the scenario of coexisting mixed s + d order parameters is indeed also realized in this electron-doped cuprate superconductor, as proposed by K.A.…”