Multi-orbital superconductivity in 4Hb-TaS2 in the dirty limit: Part I

The transition metal dichalcogenide 4Hb-TaS₂ consists of alternating single layers of octahedrally oriented T structure and trigonally oriented H structure. Separately, in their bulk form, these two structures have very different ground states: while 1T-TaS₂ is a strongly correlated insulator and a spin-liquid candidate, 2H-TaS₂ is a superconductor. The 4Hb compound also has a superconducting ground state, which has been argued to be chiral due to the onset of a μSR signal concomitant to the superconducting transition.

Thus, elucidating the interplay between these different electronic orders in stoichiometric 4Hb-TaS2, and its relationship to the alleged chiral superconducting phase, remain open questions. In part I of this talk, we present an effective tight binding model based on maximally localized Wannier functions for 4Hb-TaS2. We find a pronounced effect of the second-interlayer hopping, which makes the Fermi surfaces acquire mixed layer character. Moreover, the nonsymmorphic symmetry associated with a screw axis along the stacking direction and across the Ta atoms promotes fourfold degenerate bands at kz=pi/2.