D-wave anisotropy and coexistence of the superconducting gap and pseudogap inLa2−xSrxCuO4/Agjunctions

Abstract

We present the angle-resolved tunneling spectroscopy of ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ (LSCO)/Ag junctions. The observed tunnel conductance curves show the superconducting gap (SG) at $9\ifmmode\pm\else\textpm\fi{}1\mathrm{mV}$ for the near optimally doped samples and at $11\ifmmode\pm\else\textpm\fi{}1\mathrm{mV}$ for the underdoped samples. They also show strong decrease of conductance at a few tens of mV corresponding to the possible pseudogap (PG) for zero- and finite-angle junctions. Besides, the zero bias conductance peak (ZBCP) is observable for finite-angle junctions. The simultaneous observation of SG, PG, and ZBCP implies the coexistence of superconducting gap and pseudogap with the d-wave order parameter for LSCO.