Calendar of Events

Speaker:  Peter Orth

Abstract:  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 insight into the Berry curvature and quantum geometry of electronic Bloch states. Two-dimensional coherent THz and Raman spectroscopy are two other powerful nonlinear techniques to interrogate the low-energy excitations in quantum materials. Originally used in the radiofrequency and optical frequency range, these methods have recently become experimentally available in the THz range, where they can directly excite collective modes and elementary excitations in correlated systems. We introduce an intuitive theoretical description of these methods in terms of Liouville pathways and then present two applications: first, we theoretically show how they can directly probe the properties of fractionalized Majorana quasiparticle in Kitaev spin liquids. Second, we demonstrate that nonlinear Raman spectroscopy can unambiguously establish the presence of quantum coherence between different nematic states in a recently proposed electronic nematic liquid state in BaNi2As2.

Host:  Premi Chandra