Spectral signatures of a unique charge density wave in Ta2NiSe7

• Published in: Nature communications Vol. 14; no. 1; p. 3388
• Main Authors: Watson, Matthew D., Louat, Alex, Cacho, Cephise, Choi, Sungkyun, Lee, Young Hee, Neumann, Michael, Kim, Gideok
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 09-06-2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/119/2795; 639/766/119/995; Banded structure; Charge density waves; Electronic structure; Electrons; Emission spectroscopy; Fermi surfaces; Humanities and Social Sciences; multidisciplinary; Nesting; Science; Science (multidisciplinary); Spectral signatures; Spectroscopy; Valence band
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-39114-z

Charge Density Waves (CDW) are commonly associated with the presence of near-Fermi level states which are separated from others, or “nested", by a wavector of
q
. Here we use Angle-Resolved Photo Emission Spectroscopy (ARPES) on the CDW material Ta
2
NiSe
7
and identify a total absence of any plausible nesting of states at the primary CDW wavevector
q
. Nevertheless we observe spectral intensity on replicas of the hole-like valence bands, shifted by a wavevector of
q
, which appears with the CDW transition. In contrast, we find that there is a possible nesting at
2q
, and associate the characters of these bands with the reported atomic modulations at
2q
. Our comprehensive electronic structure perspective shows that the CDW-like transition of Ta
2
NiSe
7
is unique, with the primary wavevector
q
being unrelated to any low-energy states, but suggests that the reported modulation at
2q
, which would plausibly connect low-energy states, might be more important for the overall energetics of the problem.
The charge density wave in Ta2NiSe7 cannot be easily explained by the Fermi surface nesting mechanism. Here, by using high-resolution ARPES, the authors reveal the absence of nesting at the primary vector q, but a backfolding at q and a possible nesting at 2q, suggesting a peculiar charge density wave state.