An unexpected charge doping mechanism for quasi-one-dimensional <i>A</i>Cr₃As₃ superconductors

In the race to find topological materials, superconductivity has found renewed interest as potential hosts of Majorana Fermions. However, realizing such states is non-trivial requiring for instance Cooper pairs with finite orbital-momentum or Dirac-like dispersions in the normal state. Recently, a new family of quasi-1D superconductors A_1,2Cr₃As₃ (A= Alkali metal) was discovered which is interesting in these regards for realizing spin-triplet superconductivity and having Dirac-like crossings near E_F. However, its study has been hampered due to extreme air sensitivity and an inability to charge dope. Here, we report results of diffraction studies and DFT work on KCr₃As₃ which solve both these problems. We show that the reported growth technique inherently intercalates H into the quasi-1D CrAs tubes and that the H acts as an electron donor. Furthermore, we reveal that the reported discrepancy in sample behavior (with some superconducting and others spin-glasses) is actually due to the amount of H. This work suggests a new stoichiometry KH_1-xCr₃As₃, which is air stable and provides a charge doping mechanism. This allows for tuning between frustrated magnetism and superconductivity in a quasi-1D material as well as a potential route to reach the predicted Dirac points.