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Tuesday, September 3, 2019 at 12:20pm
700 Clark Hall
Title: Terahertz Frequency Topological Switches
In this talk I will first describe femtosecond-resolution crystallographic measurements probing dynamic switching responses driven by terahertz light pulses in topological Weyl semimetals, focusing on the 2D transition metal dichalcogenide WTe2. I will show that one can induce large amplitude interlayer shear oscillations with ~1% strain amplitudes, leading to a topologically distinct metastable phase not found under equilibrium conditions. We further show that such shear strain serves as an ultrafast, energy-efficient means to induce more robust, well-separated Weyl points or to annihilate all Weyl points of opposite chirality. After this introduction, I will also discuss new efforts investigating control of intertwined topological and ferroelectric degrees of freedom through the application of pure electric fields and through electrostatic doping. We find evidence for a new low energy ferroelectric switching mechanism through interlayer gliding and observe multiple low energy phases with distinct topological and ferroelectric signatures. This work defines new possibilities for energy efficient and high bandwidth quantum devices.
Refreshments will be served at 12pm for attendees.