title: Scattering forces from the curl of the spin angular momentum of a light field.
abstract: Light forces on small (Rayleigh) particles are usually described as the sum of two terms: the dipolar or gradient force and the scattering or radiation pressure force. The scattering force is traditionally considered proportional to the Poynting vector, which gives the direction and magnitude of the momentum flow. However, as we will show, there is an additional nonconservative contribution to the scattering force arising in a light field with nonuniform helicity. This force is shown to be proportional to the curl of the spin angular momentum of the light field. The relevance of the spin force is illustrated in the simple case of a 2D field geometry arising in the intersection region of two standing waves.
authors.affiliation: Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Albaladejo
authors.forename: Manuel I
authors.initials: MI
authors.lastname: Marqués
authors.forename: Marine
authors.initials: M
authors.lastname: Laroche
authors.forename: Juan José
authors.initials: JJ
authors.lastname: Sáenz