Orbital Hall effect and orbital edge states caused by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>s</mml:mi></mml:math> electrons

Abstract

An orbital current can be generated whenever an object has a translational degree of freedom and a rotational degree of freedom. In condensed matter physics, intra-atomic contributions to the transverse orbital transport, labeled the orbital Hall effect, rely on propagating wave packets that must consist of hybridized atomic orbitals. However, interatomic contributions have to be considered as well because they give rise to an alternative mechanism for generating orbital currents. As we show, even wave packets consisting purely of $s$ electrons can transport orbital angular momentum if they move on a cycloid trajectory. We introduce the kagome lattice with a single $s$ orbital per atom as the minimal model for the orbital Hall effect and observe the cycloid motion of the electrons in the surface states.