Andreev bound states at a cuprate grain boundary junction: A lower bound for the upper critical field

Abstract

We investigate in-plane quasiparticle tunneling across thin film grain boundary junctions (GBJs) of the electron-doped cuprate La${}_{2-x}$Ce${}_x$CuO${}_4$ in magnetic fields up to $B=16$T, perpendicular to the CuO${}_2$ layers. The differential conductance in the superconducting state shows a zero bias conductance peak (ZBCP) due to zero energy surface Andreev bound states. With increasing temperature $T$, the ZBCP vanishes at the critical temperature $T_c\approx 29$K if B=0, and at $T=12$K for B=16 T. As the ZBCP is related to the macroscopic phase coherence of the superconducting state, we argue that the disappearance of the ZBCP at a field $B_{ZBCP}(T)$ must occur below the upper critical field $B_{c2}(T)$ of the superconductor. We find $B_{ZBCP}(0)\approx 25$T which is at least a factor of 2.5 higher than previous estimates of $B_{c2}(0)$.

4 pages, 4 figures

References in corpus (3)

• Scanning tunneling spectroscopy of high-temperature superconductors
• Observation of Andreev bound states in YBaCuO/Au/Nb ramp-type Josephson junctions
• Shadow on the wall cast by an Abrikosov vortex

Cited by in corpus (3)

• Anomalous Andreev bound state in non-centrosymmetric superconductors
• Modification of Born impurity scattering near the surface of d-wave superconductors and influence of external magnetic field
• Raman light scattering study and microstructural analysis of epitaxial films of the electron-doped superconductor La_{2-x}Ce_{x}CuO_{4}