Title: Probing quasiparticle interactions and statistics through nonlinear response Abstract: In this talk, I will summarise recent theoretical work on understanding nonlinear response functions in systems with interacting quasiparticles. I will summarize hydrodynamic results for interacting integrable systems, and use this to motivate a more generally applicable formulation of response of gapped quasiparticles in terms of semiclassical spacetime trajectories. I will then move to two dimensions, using the space-time approach, and outline a proposal to use pump-probe spectroscopy as a sharp diagnostic of fractional statistics in two-dimensionally topologically ordered phases. This promises a route to a positive diagnostic of gapped quantum spin liquids even without momentum-resolved measurements. Along the way, I will comment on a surprising byproduct: the discovery of anomalous thermal broadening of two-point response functions in systems hosting mobile anyon as low-energy gapped quasiparticles. [Based on PNAS 118 (37) e2106945118 (2021), arXiv: 2208.09490, arXiv:2210.16249]  Â
Siddharth Parameswaran is associate professor of Rudolf Peierls center for theoretical physics at Oxford University. Â