Phys. Rev. Lett. 100, 227001 (2008) [4 pages]Phase Diagram of the Electron-Doped La2-xCexCuO4 Cuprate Superconductor from Andreev Bound States at Grain Boundary JunctionsReceived 17 September 2007; published 2 June 2008 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)≈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. © 2008 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.100.227001
DOI:
10.1103/PhysRevLett.100.227001
PACS:
74.25.Dw, 74.25.Op, 74.45.+c, 74.50.+r
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