CDW based memory devices
1T-TaS2 is an example of a layered transition metal dichalcogenide, which exhibits a variety of thermodynamic equilibrium states, ranging from metallic at high temperature, incommensurate and nearly commensurate charge density wave (CDW) states at intermediate temperatures and an insulating commensurate CDW Mott state below 180 Kelvin. In addition, superconductivity  and spin liquid states  are found when pressure is applied or if the material is cooled to low temperatures, respectively. Finally, a variety of long-lived metastable photo- and electrically-induced states are found, which are stable at low temperatures [3-6].
In this project, we investigate the photo- and electrically-induced topologically protected hidden (H) state, which has a few orders of magnitude lower resistivity than the thermodynamically stable CDW state and is stable at low temperatures . The transition time to the photoinduced state is below half a picosecond, making the material an ideal candidate for ultrafast low energy non-volatile memory device . We work in collaboration with the Jozef Stefan Institute (JSI) in Ljubljana, where the material is synthesized and characterized using optical methods and scanning tunneling microscopy. We are using the state-of-the-art cleanroom facilities at PSI to prepare the samples for measurements with x-rays from PSI’s accelerator-based photon sources to shine light on the nonequilibrium states in 1T-TaS2 using reciprocal space analysis.
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