Spin-valley locking in the chiral superconductor 4Hb-TaS2

Van der Waals materials offer unprecedented control of electronic properties via stacking of different types of two-dimensional materials. A fascinating frontier, largely unexplored, is the stacking of strongly correlated phases of matter. We study 4Hb-TaS₂, which naturally realizes an alternating stacking of 1T-TaS₂ and 1H-TaS₂. The former is a well-known Mott insulator, which has recently been proposed to host a gapless spin-liquid ground state. The latter is a superconductor known to also host a competing charge density wave state.  4Hb-TaS₂ is a superconductor with Tc=2.7K that was recently reported to break time reversal symmetry.

Using spin and angle-resolved photoemission spectroscopy, we find a significant charge transfer from the 1T-TaS₂ to the 1H-TaS₂ layers in good agreement with DFT calculations.

In addition, we find that the spin of quasiparticles in 4????- ??????₂ is locked to the valley degree-of-freedom leading to a non-trivial spin-texture of the Fermi-surface.