Evidence of a d- to s-Wave Pairing Symmetry Transition in the Electron-Doped Cuprate Superconductor Pr2-xCexCuO4

We present point contact spectroscopy (PCS) data for junctions between a normal metal and the electron-doped cuprate superconductor Pr_2-xCe_xCuO₄ (PCCO). For the underdoped compositions of this cuprate ( x~0.13) we observe a peak in the conductance-voltage characteristics of the point contact junctions. The shape and magnitude of this peak suggest the presence of Andreev bound states at the surface of underdoped PCCO which is evidence for a d-wave pairing symmetry. For overdoped PCCO ( x~0.17) the PCS data do not show any evidence of Andreev bound states at the surface suggesting an s-wave pairing symmetry.