Unusual electronic properties taking shape at the Bloch beamline

In a recent study, an international team led by researchers from The Pennsylvania State University in the US investigated the one-dimensional (1D) material tantalum selenide iodide (TaSe4 )2I. Its electronic properties had been theoretically predicted but not observed experimentally before the study conducted at the Bloch beamline. Evaporating iodine atoms turn out to drive unforeseen electronic changes.

Materials with unusual electronic properties such as charge density waves or topological states push the understanding of the fundamentals of quantum matter. They are also exciting candidates for the next generations of energy-efficient electronic and spintronic devices.

In the present study, the researchers found that the electronic properties of (TaSe4 )2I were different from the theoretical prediction. The band structure of a material can loosely be compared to a map of the material’s electronic properties. (TaSe4 )2I has something called Dirac bands, which is often found in this type of materials. The prediction said that the Dirac bands would split due to Weyl physics, which is not the case. The bands split with temperature, and the driver behind it is iodine atoms evaporating from the material’s surface.

“Our finding provides a platform to explore the interplay between band topology and charge density wave order in the quasi-1D material”, says Dr Cui-Zu Chang, the corresponding author of this study.

The researchers plan to continue exploring even more of the predicted properties of (TaSe4 )2I.

“Next, we will explore the axion insulator property and the possible surface Fermi arcs on the other surface of (TaSe4 )2I”, concludes Dr Chang.

Surface charge induced Dirac band splitting in 1D material (TaSe4 )2I