Non-equilibrium States and Times in 1T-TaS₂ on the Atomic Scale

PC Department Seminar
Date: Jun 30, 2026
Time: 11:00 AM (Local Time Germany)
Speaker: Yevhenii Vaskivskyi
Jozef Stefan Institute, Slovenia
Location: Building G
Room: 2.06
Host: Melanie Müller

Several non-equilibrium states in 1T-TaS2 have been discovered over the past 15 years, all of which differ significantly from its commensurate charge density wave (CDW) ground state at low-temperature equilibrium. These include the long-lived hidden domain state, which has attracted particular attention for its potential applications, an electronic amorphous state, and a range of more exotic CDW states within a single layer. All these states can be achieved with either an ultrafast optical or a short electrical excitation, providing an accessible platform for studying electronic processes in CDW materials. Understanding them is essential for uncovering the microscopic mechanisms governing metastability and dynamics, with insights that can potentially be transferred to other related systems.

In this talk, I will discuss the creation, coexistence and evolution of the non-equilibrium states studied on the nanometre scale using scanning tunnelling microscopy (STM). I will show how the created structures depend on the applied external stimulus and how the states evolve with time as a function of temperature.

The conventional STM allows only the slow dynamics of the local electronic structure to be studied, over timescales of minutes between individual measured “frames”. To gain further insights into previously unexplored timescales, I will demonstrate our latest achievements in direct measurements with sub-second time resolution, using the new Fast STM technique. This method, applied to 1T-TaS₂, allowed us to discover an unexpected stabilisation of charge motion in the Hz frequency range and film the dynamics of the CDW in real time with atomic resolution.