Orbitronics and Circulating Currents on the Molecular Scale

Orbitronics is underlying the idea that the electron’s orbital angular momentum could play a role, e.g., in information technology that is analogous to spin in Spintronics. The concept faces a challenge, however: While the time evolution of spin accumulations is governed by an exact conservation law (in the absence of spin-orbit coupling), the orbital angular momentum is not known to be.

The talk offers in its first part a brief introduction into the basic concepts highlighting, in

particular, that a huge orbital angular momentum builds up generically, whenever charge flows through molecular matter. The associated circulating currents carry a current density orders of magnitude larger than the average density flowing from source to drain – a phenomenon largely unexplored as of yet.

In its second part, we will present a theoretical analysis suggesting that the orbital angular momentum build up manifests in the magneto-optical Kerr effect (MOKE) as it has been  observed in recent measurements of the surfaces of topological insulators.

The third part of the talk is devoted to the mechanical effect of circulating currents. We will analyze in model and ab-initio calculations how the transfer of angular momentum from

the electronic current flowing along a molecule’s easy axis of rotation could drive a

molecular motor. Relations to current experiments will be discussed.