  The pairing mechanism in cuprates remains as one of the most challenging
issues in the field of condensed matter physics. The unique 3d9 electron
orbital of the Cu2+ ionic states in cuprates is supposed to be the major player
for the occurrence of superconductivity. Recently, superconductivity at about
9-15 K was discovered in infinite layer thin films of nickelate Nd1-xSrxNiO2
(x=0.1-0.2) which is believed to have the similar 3d9 orbital electrons. The
key issue concerned here is about the superconducting gap function. Here we
report the first set data of single particle tunneling measurements on the
superconducting nickelate thin films. We find predominantly two types of
tunneling spectra, one shows a V-shape feature which can be fitted very well by
a d-wave gap function with gap maximum of about 3.9 meV, another one exhibits a
full gap of about 2.35 meV. Some spectra demonstrate mixed contributions of
these two components. Our results suggest that the newly found Ni-based
superconductors play as close analogs to cuprates, and thus demonstrate the
commonality of unconventional superconductivity.
