Over-barrier photoelectron emission with Rashba spin-orbit coupling

We develop a theoretical model to calculate the quantum efficiency (QE) of photoelectron emission from materials with the Rashba spin-orbit coupling (RSOC) effect. In the low temperature limit, an analytical scaling between QE and the RSOC strength is obtained as QE /alpha(h omega - W)(2) + 2E(R)(h omega - W) - E-R(2)/3, where h omega, W, and E-R are the incident photon energy, work function, and the RSOC parameter, respectively. Intriguingly, the RSOC effect substantially improves the QE for strong RSOC materials. For example, the QE of Bi2Se3 and Bi/Si (111) increases, by 149% and 122%, respectively, due to the presence of strong RSOC. By fitting to the photoelectron emission characteristics, the analytical scaling law can be employed to extract the RSOC strength, thus offering a useful tool to characterize the RSOC effect in materials. Importantly, when the traditional Fowler-Dubridge model is considered, the extracted results of the prefactor a(1) in QE may substantially deviate from the actual values by similar to 90%, thus highlighting the importance of employing our model to analyze the photoelectron emission especially for materials with strong RSOC. These findings provide a theoretical foundation for the design of photoemitters using Rashba spintronic materials.