Disorder and diffuse scattering in single-chirality (TaSe4)2I crystals

Jacob A. Christensen, Simon Bettler, Kejian Qu, Jeffrey Huang, Soyeun Kim, Yinchuan Lu, Chengxi Zhao, Jin Chen, Matthew J. Krogstad, Toby J. Woods, Fahad Mahmood, Pinshane Y. Huang, Peter Abbamonte, Daniel P. Shoemaker

Research output: Contribution to journalArticlepeer-review


The quasi-one-dimensional chiral compound (TaSe4)2I has been extensively studied as a prime example of a topological Weyl semimetal. Upon crossing its phase transition temperature TCDW≈263K, (TaSe4)2I exhibits incommensurate charge density wave (CDW) modulations described by the well-defined propagation vector ∼(0.05,0.05,0.11), oblique to the TaSe4 chains. Although optical and transport properties greatly depend on chirality, there is no systematic report about chiral domain size for (TaSe4)2I. In this study, our single-crystal scattering refinements reveal a bulk iodine deficiency, and Flack parameter measurements on multiple crystals demonstrate that separate (TaSe4)2I crystals have uniform handedness, supported by direct imaging and helicity-dependent terahertz emission spectroscopy. Our single-crystal x-ray scattering and calculated diffraction patterns identify multiple diffuse features and create a real-space picture of the temperature-dependent (TaSe4)2I crystal structure. The short-range diffuse features are present at room temperature and decrease in intensity as the CDW modulation develops. These transverse displacements, along with electron pinning from the iodine deficiency, help explain why (TaSe4)2I behaves as an electronic semiconductor at temperatures above and below TCDW, despite a metallic band structure calculated from density functional theory of the ideal structure.

Original languageEnglish (US)
Article number034202
JournalPhysical Review Materials
Issue number3
StatePublished - Mar 2024

ASJC Scopus subject areas

  • General Materials Science
  • Physics and Astronomy (miscellaneous)


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