Colloquium – Matthew Day
Matthew Day, Columbia University
Optical Control over Topology in Quantum Materials
The geometric texture of quantum states can shape macroscopic behaviors. In ‘topological’ systems, special geometric textures can lead to features such as dissipation-less energy transport or fractional quasi-particles which could revolutionize our computing and communication technologies. Therefore, a current experimental challenge is controlling these topological properties in real-time. Addressing this challenge would bridge the gap between fundamental physics and practical application while yielding new insights into the principles underlying such exotic properties.
Using ultrafast laser pulses, we manipulate topological properties through Floquet engineering. This technique works by breaking symmetries with intense light to create and control photon-dressed states which can “rewrite” quantum geometry in real-time. In experiments on the type-II Weyl semimetal Td-MoTe2 embedded within ultrafast optoelectronic circuits, we observed a light-induced anomalous Hall effect that defies conventional nonlinear optical expectations. This discovery, supported by first-principles simulations, suggests the formation of a magnetic Floquet-Weyl state—a new topological phase induced by breaking time-reversal symmetry. Our findings demonstrate that light can serve as a powerful tool to change material topology on ultrafast timescales. Looking ahead, I will discuss future directions for controlling both static and dynamic properties of quantum materials embedded in optoelectronic devices, paving the way for fundamental discoveries and transformative technologies in computing, sensing, and beyond.
Monday, February 24, 2025
Talk: 3:10 PM, Stevenson Center 4327
Light refreshments available in the lobby at 2:50 PM
Host: K Varga