Anomalous transport and hidden collective modes in clean quantum materials

Clean quantum materials can host transport regimes and collective excitations that are not captured by ordinary Drude, ballistic, or conventional hydrodynamic descriptions. In this talk I will discuss how electron–electron interactions, conservation laws, and long-lived Fermi-surface deformations produce anomalous transport signatures in low-dimensional systems. I will begin with tomographic electron transport, where odd-parity deformations of the Fermi surface acquire anomalously long lifetimes, and show how weak magnetic fields suppress this regime by mixing angular harmonics. I will then discuss how nonlinear thermoelectric response can probe these hidden long-lived modes in topological Fermi liquids. I will also briefly connect this transport perspective to plasmon-assisted photodetection in graphene, where nonlinear optical response generates pseudo-Euler dynamics for collective electronic variables beyond the regime of conventional hydrodynamics. As an outlook, I will discuss a Fermi-liquid model of d-wave altermagnets that predicts spin-carrying anisotropic demon modes and their hybridization into Fano-demon states. The common theme is the use of transport, optical response, and nonlinear spectroscopy to reveal hidden many-body structure in clean quantum materials, from anomalously long-lived Fermi-surface modes to dark collective excitations and beyond-hydrodynamic