Structural instability and magnetism of superconducting KCr3As3

We find a lattice instability in the superconductor ${\mathrm{KCr}}₃{\mathrm{As}}₃$, corresponding to a distortion of the Cr metallic wires in the crystal structure. This distortion couples strongly to both the electronic and magnetic properties, in particular by making the electronic structure much more nearly one dimensional, and by shifting the compound away from magnetism. We discuss the implications of these results in the context of the possibly unconventional superconductivity of this phase.