Pulling extremely anisotropic lossy particles using light without intensity gradient

We study the effect of pulling optical force acting on a nonmagnetic anisotropic bead in electromagnetic fields without intensity gradient. Extreme anisotropy can be realized by a hyperbolic metamaterial made of metal-dielectric multilayers. We find that a passive anisotropic Rayleigh particle cannot be pulled by the electromagnetic beam without intensity gradient and the nonparaxial incident beams can exert backward negative force acting on anisotropic dipole spheres. We investigate the validity of the dipole approximation and establish the conditions for pulling hyperbolic-metamaterial particles. It is important to note that the loss in hyperbolic metamaterial does not suppress the effect of pulling force. We notice that the nonradial components of the permittivity tensor strongly affect the optical force and propose the way of material engineering to ensure the optical pulling.