  Time reversal symmetry breaking in superconductors, resulting from external
magnetic fields or spontaneous magnetization, often leads to unconventional
superconducting properties. In this way, a conventional
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, characterized by the Cooper
pairs with nonzero total momentum, may be realized by the Zeeman effect caused
from external magnetic fields. Here, we report the observation of
superconductivity in a few-layer antiferromagnetic insulator CrOCl by utilizing
superconducting proximity effect with NbSe2 flakes. The superconductivity
demonstrates a considerably weak gap of about 0.12 meV and the in-plane upper
critical field reveals as behavior of the FFLO state at low temperature. Our
first-principles calculations indicate that the proximitized superconductivity
may exist in the CrOCl layer with Cr vacancies or line-defects. Moreover, the
FFLO state could be induced by the inherent larger spin splitting in the CrOCl
layer. Our findings not only demonstrate the fascinating interaction between
superconductivity and magnetism, but also provide a possible path to construct
FFLO state by intrinsic time reversal symmetry breaking and superconducting
proximity effect.
