  Optical isolation enables nonreciprocal manipulations of light with broad
applications in optical communications. Optical isolation by rotating
structures has drawn considerable attention due to its magnetic-free nature and
unprecedented performance. Conventional rotation-based optical isolation relies
on the use of bulky cavities hindering applications in subwavelength photonics.
Here, we propose a novel mechanism of optical isolation by integrating the
unique dispersion of a hyperbolic metamaterial with the transverse spin-orbit
interaction of evanescent waves. We show that rotation of a subwavelength
hyperbolic nanoparticle breaks the time-reversal symmetry and yields two
resonant chiral modes that selectively couple to the transverse spin of
waveguide modes. Remarkably, the transverse spin-orbit interaction can give
rise to unidirectional coupling and $>95\%$ isolation of infrared light at an
experimentally feasible rotation speed. Our work fuses the two important fields
of optical isolation and photonic spin-orbit interactions, leading to
magnetic-free yet compact nonreciprocal devices for novel applications in
optical communications, chiral quantum optics, and topological photonics.
