Nematicity and superconductivity in orthorhombic superconductor Na0.35(C3N2H10)0.426Fe2Se2

Na-0.35(C3N2H10)(0.426)Fe2Se2 exhibits a large orthorhombic distortion at room temperature without magnetic ordering, hence providing an ideal platform to investigate the correlation between nematicity and superconductivity. We show that its nematicity is stabilized by "nematic" ordered 1,3-diaminopropane (1,3-DIA) molecules in between the FeSe layers, and the C2 twofold rotational symmetry is preserved down to 10 K without phase transition. The superconductivity occurs at 46.5 K even though the orthorhombic distortion is much larger than that for beta-FeSe and most of the other pnictide superconductors at low temperatures. First principles calculations reveal that this "artificial" orthorhombic distortion has a selective effect on the band structure, which behaves differently on splitting the iron 3d(xz) and 3d(yz), orbitals around the Gamma and M points in the Brillouin zone. Our finding strongly supports that the nematic state is irrelevant to the emergent superconductivity, at least in high-T-c iron selenide superconductors.