Title: Probing and Controlling Quantum Materials with Terahertz Light
Quantum materials often harbor emergent orders and phases that reveal themselves at low-energy scales, around 1 to 10 meV. To investigate these collective behaviors, we turn to the terahertz energy regime—a crucial window for probing and controlling quantum phenomena. In this talk, I will present our latest breakthroughs in unraveling the superconducting gap structure of the newly discovered unconventional nickelate superconductors— a topic that has sparked intense debate and remains unresolved. Using both linear and nonlinear terahertz spectroscopy, we uncover compelling evidence pointing to a d-wave gap structure in these materials. We further demonstrate that this d-wave superconductivity exists within the weak-coupling regime and the dirty limit, providing key insights that could steer future research in this field. Expanding beyond understanding, I will broaden the discussion to the manipulation of quantum materials through light. I will show how we harness intense terahertz pulses to drive the electronic structure of a Dirac semimetal, leading to the observation of record-breaking terahertz high harmonics. Our findings position topological materials as promising platforms for delving into high harmonic generation and strong-field physics.Title: Â