Résumé
In this work, we investigate the potential of nonreciprocal platforms to control and enhance surface waves and nanoscale forces/torques in unconventional ways. We consider a gyrotropic magnetized plasma as a model system that can be designed to exhibit either weak or strong forms of nonreciprocity, as well as elliptical or hyperbolic modal dispersion. We show that this continuum material platform supports ultra-narrow unidirectional surface-plasmon-polariton beams, tunable via the emitter operational frequency or the cyclotron frequency of the biased plasma. In addition, we also investigate the effect of launching such unidirectional surface modes on the emitter itself. We show that, due to the asymmetric release of angular momentum, a non-trivial optical torque is exerted a generic dipolar emitter. We obtain a closed-form expression for this optical torque in terms of the system Green function valid for any three-dimensional, inhomogeneous, dissipative, dispersive, nonreciprocal, and bianisotropic structure. Advanced material platforms of this type may provide new degrees of freedom to control the orientation and rotation of nano-objects and optically-driven rotary nanomachines.