Temperature-dependent Fermi surface of 2H-TaSe2 driven by competing density wave order fluctuations

TL;DR

This study investigates how the Fermi surface of 2H-TaSe2 evolves with temperature, revealing nonmonotonic changes linked to competing charge density wave fluctuations, which may explain pseudogap behavior in related materials.

Contribution

The paper provides high-resolution ARPES measurements and tight-binding modeling to detail the temperature-dependent Fermi surface and its relation to charge density wave fluctuations in 2H-TaSe2.

Findings

Nonmonotonic temperature dependence of the Fermi surface shape.

Incommensurability parameter matches charge modulation data.

Fermi surface changes linked to competing charge density wave fluctuations.

Abstract

Temperature evolution of the 2H-TaSe2 Fermi surface (FS) is studied by high-resolution angle-resolved photoemission spectroscopy (ARPES). High-accuracy determination of the FS geometry was possible after measuring electron momenta and velocities along all high-symmetry directions as a function of temperature with subsequent fitting to a tight-binding model. The estimated incommensurability parameter of the nesting vector agrees with that of the incommensurate charge modulations. We observe detectable nonmonotonic temperature dependence of the FS shape, which we show to be consistent with the analogous behavior of the pseudogap. These changes in the electronic structure could stem from the competition of commensurate and incommensurate charge density wave order fluctuations, explaining the puzzling reopening of the pseudogap observed in the normal state of both transition metal dichalcogenides and high-Tc cuprates.