Observation of Andreev bound states in bicrystal grain-boundary Josephson junctions of the electron doped superconductor LaCeCuO

Abstract

We observe a zero-bias conductance peak (ZBCP) in the ab-plane quasiparticle tunneling spectra of thin film grain-boundary Josephson junctions made of the electron doped cuprate superconductor LaCeCuO. An applied magnetic field reduces the spectral weight around zero energy and shifts it non-linearly to higher energies consistent with a Doppler shift of the Andreev bound states (ABS) energy. For all magnetic fields the ZBCP appears simultaneously with the onset of superconductivity. These observations strongly suggest that the ZBCP results from the formation of ABS at the junction interfaces, and, consequently, that there is a sign change in the symmetry of the superconducting order parameter of this compound consistent with a d-wave symmetry.

9 pages, 7 figures; December 2004, accepted for publication in Phys. Rev. B

References in corpus (8)

• Andreev bound states in high-$T_c$ superconducting junctions
• Evidence of a d to s-wave pairing symmetry transition in the electron-doped cuprate superconductor Pr${}_{2-x}$Ce${}_x$CuO${}_4$
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• Possible pseudogap behavior of electron doped high-temperature superconductors
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• Point contact spectroscopy of the electron-doped cuprate superconductor Pr{2-x}Ce{x}CuO4: The dependence of conductance-voltage spectra on cerium doping, barrier strength and magnetic field
• Shadow on the wall cast by an Abrikosov vortex
• Disordered Josephson Junctions of d-Wave Superconductors

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