Folded pseudochiral Fermi surface in 4Hb-TaSe2 from band hybridization with a charge density wave

Abstract Stacking of strongly-correlated 2D materials is opening the possibility to demonstrate novel electronic or magnetic ordering phenomena. In this regard the intrinsic polytypism of tantalum dichalcogenides has emerged as a platform to generate clean and controllable material interfaces. Here, we report on the Fermi surface of 4 Hb -TaSe 2 , a polytype which consists of alternately stacked layers with octahedral ( T ) and trigonal prismatic ( H ) coordination of tantalum in the Se-Ta-Se layers. The material is known to host a charge density wave (CDW) phase with star clusters in the T -layers, intercalated by metallic H -layers, but its momentum resolved electronic structure remains undetermined. Using selective area angle resolved photoemission spectroscopy on the T termination combined with ab initio calculations, we unveil a finely structured Fermi surface arising from band folding in the reconstructed Brillouin zone caused by the CDW star clusters. The star-shaped Fermi surface is rotated away from the high-symmetry directions of the normal phase, and exhibits pseudochirality. Theoretical analysis supports the metallic nature of the system and interlayer interactions leading to hybridization. The work provides a detailed overview on the impact of band hybridization with the CDW on the Fermi surface of a material for new phases of quantum matter.