Andreev reflections and tunneling spectroscopy on underdoped NCCO (x = 0.15)

Abstract

Andreev-reflection and tunneling studies have been carried out on a single crystal of underdoped Nd1.85Ce0.15CuO4-d (NCCO) by using Ag, Pt-Ir and Nb tips to clarify the symmetry of its order parameter. Surprisingly, we observed in the NCCO, on the one hand, the Josephson current (with Nb tip) which indicates the presence of s-wave order parameter, on the other hand, a zero-bias conductance peak (with Ag tip) which is a manifestation of d-wave order parameter. In addition, we find the presence of two distinct energy scales in the underdoped NCCO: the smallest energy scale is associated with the Andreev gap and c-axis tunneling gap, and the second scale corresponds to the maximum in-plane tunneling gap. It seems that the phenomenon of superconductivity in electron- and hole-doped cuprates can be understood within a common scheme.

10 pages including 4 figures; to appear in Europhysics Letters

References in corpus (4)

• Anomalous Low Temperature Behavior of Superconducting Nd(1.85)Ce(0.15)CuO(4-y)
• The pseudogap in Bi2212 single crystals from tunneling measurements: a possible evidence for the Cooper pairs above Tc
• The Symmetries of the Order Parameters for Pairing and Phase Coherence in Hole-Doped Cuprates
• Nonequilibrium Campbell length: probing the vortex pinning potential

Cited by in corpus (13)

• Imaging the Two Gaps of the High-TC Superconductor Pb-Bi2Sr2CuO6+x
• Evidence of a d to s-wave pairing symmetry transition in the electron-doped cuprate superconductor Pr${}_{2-x}$Ce${}_x$CuO${}_4$
• Evidence for nodal quasiparticles in electron-doped cuprates from penetration depth measurements
• Distinct Pairing Symmetries in $N{d}_{1.85}C{e}_{0.15}Cu{O}_{4-y}$ and $L{a}_{1.89}S{r}_{0.11}Cu{O}_4$ Single Crystals: Evidence from Comparative Tunnelling Measurements
• 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
• Observation of Andreev bound states in bicrystal grain-boundary Josephson junctions of the electron doped superconductor LaCeCuO
• Mechanism of High-Tc Superconductivity Based Mainly on Tunneling Measurements in Cuprates
• Quasi-One-Dimensional Topological-Excitation Liquid in Bi2212 from Tunneling Spectroscopy
• c-Axis Phase Coherence and Spin Fluctuations in Cuprates
• Andreev bound states at a cuprate grain boundary junction: A lower bound for the upper critical field
• Theory of point contact spectroscopy in electron-doped cuprates
• Determination of the Coherence Length and the Cooper-Pair Size in Unconventional Superconductors by Tunnelling Spectroscopy
• Andreev reflection off a fluctuating superconductor in the absence of equilibrium