The field of photoinduced phase transitions (PIPT) attracts huge interest being the powerful tool for generation of new states of matter on ultrashort timescale. One of the special cases of PIPT, insulator-metal transitions, are of particular importance for industry, as they potentially can provide the ground for development of novel types of memory devices with much improved performance. While the switching speeds for PIPT in strongly correlated materials are usually high (~1-100 ps), stability of such photoinduced states, in most cases, is very low (~10-10-10-3 s) limiting their practical application.
From this perspective, recently discovered photo- and current-induced transition to conductive state in 1T-TaS2 is unique example of accessing long-lived hidden (H) order [1, 2].
The phase transition in this material can be triggered by single ultrashort laser or by short electrical pulse at low temperature. By employing optical time-resolved multi-pulse technique, we show that the lattice responds to the excitation within 0.5 ps, which is equivalent to single period of breathing mode of charge density wave (CDW) in the system. Electronic subsystem thermalizes in the new state in less than 5 ps.
Both low-temperature ground and the H phase are charge-density-wave-ordered states. Transient photodoping, created by laser pulse causes reorganization of the homogenous commensurate CDW order into the new textured phase with modified wavevector, which is stabilized by topological defects.
I will present current understanding of switching mechanism, microscopic structure as well as main properties of the new photoinduced state.
The work was supported by ERC ADG Trajectory (GA320602).
. L. Stojchevska et al. Science 344, 6180 (2014).
. I. Vaskivskyi et al. Nature Communications 7, 11442 (2016).