A time-domain phase diagram of metastable states in a charge ordered quantum material

Jan Ravnik
Paul Scherrer Institut (Switzerland)

Abstract:

Metastable self-organized electronic states in quantum materials are typically formed through phase transitions under non-equilibrium conditions and the final state is reached through processes that span a large range of timescales. Conventionally, phase diagrams are thought of as static, without temporal evolution. However, many functional properties of materials arise as a result of complex temporal changes in the material. Here, by using time-resolved optical techniques and femtosecond-pulse-excited scanning tunneling microscopy (STM), we track the evolution of the metastable states in the quasi-two-dimensional dichalcogenide 1T-TaS₂. We map out its temporal phase diagram using the photon density and temperature as control parameters on timescales ranging from 10^-12 to 10³ s. The introduction of a time-domain axis in the phase diagram enables us to follow the evolution of metastable emergent states, and opens the way to understanding of the complex ordering processes in metastable materials.

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