# Role of transverse momentum currents in optical Magnus effect in the free space 

Hailu Luo, Shuangchun Wen, ∗ Weixing Shu, and Dianyuan Fan 

Key Laboratory for Micro/Nano Opto-Electronic Devices of Ministry of Education, Hunan University, Changsha 410082, China 

(Dated: June 2, 2018) 

## Abstract 

We establish a general vector field model to describe the role of transverse momentum currents in optical Magnus effect in the free space. As an analogy of mechanical Magnus effect, the circu- larly polarized wavepacket in our model acts as the rotating ball and its rotation direction depends on the polarization state. Based on the model we demonstrate the existence of a novel optical polarization-dependent Magnus effect which is significantly different from the conventional optical Magnus effect in that light-matter interaction is not required. Further, we reveal the relation be- tween transverse momentum currents and optical Magnus effect, and find that such a polarization- dependent rotation is unavoidable when the wavepacket possesses transverse momentum currents. The physics underlying this intriguing effect is the combined contributions of transverse spin and orbital currents. We predict that this novel effect may be observed experimentally even in the propagation direction. These findings provide further evidence for the optical Magnus effect in the free space. 

PACS numbers: 42.25.-p, 42.79.-e, 41.20.Jb 

Keywords: optical Magnus effect, transverse momentum currents, spin angular momentum, orbital angular momentum 

