Speaker
Description
The ponderomotive force is an effective static force that a particle feels in an oscillating field. We generalize this notion to the static force felt by the collective degrees of freedom in periodically driven quantum many-body systems [PRB 110, 104301 (2024)]. It may be used to predict their non-equilibrium steady states. We show that the ponderomotive force from the uniform incident light may be used to induce exciton condensates, to generate superconductivity, to manipulate systems with charge/spin/excitonic orders, and to tune many-body phases in optically driven cavities.
In the second part of the talk, we show that the light induced static forces on electronic order parameters can be nonconservative [arXiv:2608.29122 (2026)], which originate from dissipation, i.e., optical absorption. This effect is demonstrated in two nontrivial examples. In excitonic insulators, via interband excitations, the light field generates a nonconservative force on the phase of the excitonic order parameter. This force leads to an acceleration of the phase, which manifests as a shift of the photon emission peak from an exciton condensate. In materials with an incommensurate charge density wave, a propagating light field generates a nonconservative force on the phase of its order parameter. It drives the charge density wave into sliding motion, leading to a DC electric current via topological Thouless pumping.