K-resolved susceptibility function of 2H-TaSe₂ from angle-resolved photoemission

The connection between the Fermi surface and charge-density-wave (CDW) order is revisited in 2H-TaSe₂. Using angle-resolved photoemission spectroscopy, ab initio band-structure calculations, and an accurate tight-binding model, we develop the empirical k-resolved susceptibility function, which we use to highlight states that contribute to the susceptibility for a particular q vector. We show that although the Fermi surface is involved in the peaks in the susceptibility associated with CDW order, it is not through conventional Fermi surface nesting, but rather through finite energy transitions from states located far from the Fermi level. Comparison with monolayer TaSe₂ illustrates the different mechanisms that are involved in the absence of bilayer splitting.