Studying Charge Density Wave State Onset in 1T-TiSe₂

The transition metal dichalcogenide 1T-TiSe₂ is a quasi-two-dimensional, layered, charge density wave (CDW) compound. Each layer is composed of TiSe₆ octahedra and neighboring layers are stacked along the c-axis bound together by van der Waals forces. Near ~200 K, 1T-TiSe₂ enters a CDW state. This CDW state is characterized by a commensurate 2a₀ × 2a₀ × 2c₀ superstructure. It has also been reported, though debated, that the CDW order is chiral in nature.

Here we present our scanning tunneling microscopy (STM) measurements on 1T- TiSe₂ at 9K (well-below the CDW transition) and near the CDW transition at ~200K, investigating its onset. Within this context, we discuss the nature of its chirality.