title: Phase diagram of the electron-doped La2-xCexCuO4 cuprate superconductor from Andreev bound states at grain boundary junctions.
abstract: We use quasiparticle tunneling across La2-xCexCuO4 grain boundary junctions to probe the superconducting state and its disappearance with increasing temperature and magnetic field. A zero bias conductance peak due to zero energy surface Andreev bound states is a clear signature of the phase coherence of the superconducting state. Hence, such a peak must disappear at or below the upper critical field Bc2(T). For La2-xCexCuO4 this approach sets a lower bound for Bc2(0) approximately 25 T which is substantially higher than reported previously. The method of probing the superconducting state via Andreev bound states should also be applicable to other cuprate superconductors.
authors.affiliation: Physikalisches Institut-Experimentalphysik II and Center for Collective Quantum Phenomena, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany. wagenknecht@uni-tuebingen.de
authors.forename: M
authors.initials: M
authors.lastname: Wagenknecht
authors.forename: D
authors.initials: D
authors.lastname: Koelle
authors.forename: R
authors.initials: R
authors.lastname: Kleiner
authors.forename: S
authors.initials: S
authors.lastname: Graser
authors.forename: N
authors.initials: N
authors.lastname: Schopohl
authors.forename: B
authors.initials: B
authors.lastname: Chesca
authors.forename: A
authors.initials: A
authors.lastname: Tsukada
authors.forename: S T B
authors.initials: ST
authors.lastname: Goennenwein
authors.forename: R
authors.initials: R
authors.lastname: Gross