Dragan Mihailovic (SIMES Seminar)

Date(s) - Jun 8 2016
11:30 AM - 12:30 PM

Sierra Room, Bldg 40, Room R125


From metal to insulator – in a single beat of a collective mode in 1T-TaS2.

Dragan Mihailovic+

Jozef Stefan Institute, Ljubljana, Slovenia


States which form under non-equilibrium conditions are of fundamental interest in the physics of phase transitions, with famous analogues in cosmology (e.g. the process of Baryogenesis and false vacuum states). They are currently also of great practical interest for ultrafast memory devices. In the quasi-two-dimensional dichalcogenide, 1T-TaS2, conditions for the formation of a hidden (H) false vacuum state are created by a transient particle-hole asymmetry. Microscopically, frozen H-state STM images show a transition from beautifully ordered commensurate polaron crystal to textured electronic order with sharp threshold behavior as a function of photoexcitation intensity. Remarkably, specially designed femtosecond timescale optical experiments show that the transition occurs within a single oscillation of the collective amplitude mode, enabling coherent optical control of the I-M transition.

While the non-equilibrium transition can be understood quite well within time-dependent Ginzburg Landau theory using time-dependent potentials, our microscopic understanding of the metastable H state includes an interplay of intra-layer Mott physics, an underlying charge-density wave instability, spin-orbit coupling and inter-layer “orbitronic” ordering, but is relatively poorly understood.


+This work was performed in collaboration with Igor Vaskivskyi, Tomaz Mertelj, Damjan Svetin, Ian A. Mihailovic, Yaroslav Gerasimenko, Patrick Kirchmann (Stanford) and Serguei Brazovskii (Orsay).