Tunneling study on the electron-doped superconductorNd1.85Ce0.15CuO4−y

From tunneling measurements for the electron-doped cuprate oxide superconductor ${\mathrm{Nd}}_{2\mathrm{-}\mathrm{x}}$ ${\mathrm{Ce}}_{\mathrm{x}}$ ${\mathrm{CuO}}_{4\mathrm{-}\mathrm{y}}$, we obtained the superconducting energy gap of 2Δ=8 meV with $T_c$=17–18 K. This result leads to the value of 2Δ/${\mathrm{kT}}_c$=5.2–5.5, which is close to or somewhat larger than that for ${\mathrm{La}}_{2\mathrm{-}\mathrm{x}}$ ${\mathrm{Sr}}_{\mathrm{x}}$ ${\mathrm{CuO}}_4$ but slightly smaller than that for ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CuO}}_{\mathrm{y}}$. DOI: http://dx.doi.org/10.1103/PhysRevB.40.7364 © 1989 The American Physical Society