Angle-resolved photoemission spectroscopy study of the charge density wave order in layered semiconductor EuTe4

TL;DR

This study uses angle-resolved photoemission spectroscopy to explore the charge density wave phenomena in EuTe4, revealing a nesting vector, persistent anisotropic gaps, and unusual temperature dependence, advancing understanding of quasi-2D CDW materials.

Contribution

It provides detailed experimental insights into the Fermi surface nesting, gap behavior, and band interactions in EuTe4, a quasi-2D CDW compound, which were previously not well understood.

Findings

Fermi surface nesting vector q ~ 0.67 b* drives CDW formation.

Large anisotropic CDW gap persists at 300 K, indicating semiconductor behavior.

CDW gap exhibits non-monotonic temperature dependence and an additional higher-energy gap.

Abstract

Layered tellurides have been extensively studied as a platform for investigating the Fermi surface (FS) nesting-driven charge density wave (CDW) states. EuTe4, one of quasi-two-dimensional (quasi-2D) binary rare-earth tetratellurides CDW compounds, with unconventional hysteretic transition, is currently receiving much attention. Here, the CDW modulation vector, momentum and temperature dependence of CDW gaps in EuTe4 are investigated using angle-resolved photoemission spectroscopy. Our results reveal that (i) a FS nesting vector q ~ 0.67 b* drives the formation of CDW state, (ii) a large anisotropic CDW gap is fully open in the whole FS, and maintains a considerable size even at 300 K, leading to appearance of semiconductor properties, (iii) an abnormal non-monotonic increase of CDW gap in magnitude as a function of temperature, (iv) an extra, larger gap opens at a higher binding energy due to the interaction between the different orbits of the main bands.