Microscopic mechanism for the Rashba spin-band splitting: Perspective from formation of local orbital angular momentum

Abstract

Despite its history, the microscopic mechanism for the Rashba spin-band splitting was not well understood. It was very recently pointed out that local orbital angular momentum (OAM) plays a crucial role in the Rashba effect. Subsequently, an effective Hamiltonian was proposed. The proposed Hamiltonian was found to not only explain all the known aspects of the Rashba phenomena but also correctly predict properties that were not known before. It brings about shifts from spin-based to OAM-based approaches in the understanding of the Rashba effect. Here, we review the developments in the new approach. Starting from a brief introduction, issues in the conventional understanding of the Rashba effect are discussed. It is then described in detail that local OAM results in significant electrostatic energy which along with the atomic spin–orbit coupling explains the Rashba effect. Experimental evidences for the existence of OAM from circular dichroism in angle resolved photoemission, thus the validity of the model, are also reviewed.