Hydrogen doping induced px±ipy triplet superconductivity in quasi-one-dimensional K2Cr3As3

Quasi-one-dimensional Cr-based superconductor ${\mathrm{K}}_2{\mathrm{Cr}}_3{\mathrm{As}}_3$ has aroused great research interest due to its possible triplet pairing symmetry. Recent experiments have shown that incorporating hydrogen into ${\mathrm{K}}_2{\mathrm{Cr}}_3{\mathrm{As}}_3$ would significantly change its electronic and magnetic properties. Hence, it is necessary to investigate the impact of hydrogen doping in the pairing symmetry of this material. Employing the hydrogen as a nontrivial electron doping, our calculations show that the system exhibits $p_x\pm i{p}_y$-wave pairing symmetry under specific hydrogen doping, in contrast with the $p_z$-wave one obtained without hydrogen. Specifically, we adopt the random-phase-approximation approach based on a six-band tight-binding model equipped with multiorbital Hubbard interactions to study the hydrogen doping dependence of the pairing symmetry and superconducting $T_c$. Under the rigid-band approximation, our pairing phase diagram shows that the spin-triplet pairing covers the hydrogen doping regime $x\in (0,0.7)$. In particular, the $T_c\sim x$ curve shows a peak at the 3D-quasi-1D Lifshitz transition point, and the pairing symmetry near this doping level is $p_x\pm i{p}_y$. The physical origin of this pairing symmetry is that the density of states is mainly contributed from momenta with large $k_x\left(k_y\right)$ components on the Fermi surface. Due to the three-dimensional characteristic of the real material, this $p_x\pm i{p}_y$-wave pairing possesses a point-node gap. We further provide experiment predictions to identify this triplet $p_x\pm i{p}_y$-wave superconductivity.