Antiferromagnetic insulating state in quasi-one-dimensional K2Cr3As3H

Quasi-one-dimensional (Q1D) Cr-based pnictide K2Cr3As3 exhibits superconductivity probably with spin-triplet pairing. It is of fundamental importance to explore the parent compound from which superconductivity emerges. Here we report the synthesis, crystal structure, physical properties, and density functional theory (DFT) calculations of (nearly) fully hydrogenized K2Cr3As3H. It is found that the intercalation of hydrogen in K2Cr3As3 leads to absence of metallicity as well as superconductivity. An antiferromagnetic transition nearby room temperature is evidenced from the measurements of magnetic susceptibility and heat capacity. The antiferromagnetic insulating state can be reproduced by the DFT calculations, which show a novel non-collinear co-planar magnetic order. Our result sheds light on the mechanism of unconventional superconductivity in Q1D Cr-based superconductors.