Ritesh Agarwal1
University of Pennsylvania1
Ritesh Agarwal1
University of Pennsylvania1
We will start by discussing nonlocal photogalvanic spectroscopies where the photon momentum of engineered optical beams can be utilized to probe quantum materials (e.g., Weyl semimetals and supertwisted spirals of 2D materials) uncovering new aspects of light-matter interactions.Specifically, we will discuss the nonlinear optical Hall effect in self-assembled supertwisted WS<sub>2</sub> system formed by a screw-dislocation-driven mechanism. The optical Hall current reflects the structural handedness of the supertwisted system, and an unusual photon-momentum dependence of the nonlinear optical response in the moire potential was observed. Furthermore, signatures of thickness-dependent exciton-polaritons and the associated strong photon momentum-lattice interaction dependent photocurrent response were measured, which suggest a fundamentally altered light-matter interaction in 3D moire systems. Our response function theory can explain the origin of the photon momentum dependent nonlinear response, revealing new observables of the system going beyond Berry curvature and other conventional band geometrical quantities. Our study seamlessly connects 2D and 3D twistronics and provides a bridge connecting the electrons and photons by overcoming their significant length scale differences in conventional systems. These measurements also demonstrate the versatility of 3D moire systems for exploring new aspects of light–matter interaction phenomena in condensed matter systems, which are important in realizing extreme large optical nonlinearities for a variety of quantum and classical photonic applications.