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

TL;DR

This paper develops a k-resolved susceptibility function for 2H-TaSe2 using ARPES, revealing that charge-density wave order arises from finite energy transitions rather than Fermi surface nesting.

Contribution

It introduces an empirical k-resolved susceptibility method combining ARPES and theoretical models to analyze CDW mechanisms in 2H-TaSe2.

Findings

Fermi surface involved in susceptibility peaks but not through nesting

Finite energy transitions from states far from Fermi level drive CDW

Different mechanisms in monolayer versus bilayer TaSe2

Abstract

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.