Speaker
Description
The nonlinear response of quantum materials contains a wealth of information that is often hidden in the linear regime. Examples include second-harmonic generation as a sensitive probe of electronic symmetry, and higher-order conductivities that provide insights into the quantum geometry of Bloch states and their Berry curvature distribution. Two-dimensional coherent THz and Raman spectroscopy are two other powerful nonlinear probes of low-energy excitations in quantum materials, which have recently become available in several labs. We review experimental progress and introduce an intuitive theoretical description of these methods in terms of Liouville quantum pathways. We then theoretically show how they can directly probe quasiparticle properties in the Kitaev honeycomb spin liquid and provide direct evidence for the emergence of localized Majorana excitations trapped by vison pairs.
