Dynamics of Orbital Angular Momentum in Centrosymmetric Systems

Abstract

Roles of orbital angular momentum have received a great attention in the spintronics community because of its large Hall effect in general contexts. However, detection of the orbital angular momentum transport is very challenging due to similarity of spin and orbital angular momenta. In this work, we reveal a fundamental difference between the orbital and spin angular momentum operators, in regard to the anticommutator algebra. The different algebraic properties result in oscillatory dynamics of orbital angular momentum, which is similar to the spin Hanle oscillation, but not requiring any symmetry breaking such as an external magnetic field. We identify a physical quantity named orbital torsion, which mediates the orbital Hanle oscillation. The relation between the orbital torsion and the orbital angular momentum is similar to that in the classical torsion pendulum (Fig. 1). Since the orbital torsion and related phenomena have no spin counterpart, the orbital torsion would be greatly helpful for experimental distinction of orbital angular momentum from spin angular momentum. We also propose several methods to detect the orbital torsion transport.