First-principles Wannier Function Approach to Rashba Effect

In various two-dimensional electronic systems, Rashba effect arises due to the spin-orbit interaction. Rashba coefficients α_R, strength coefficients of Rashba effect, are key ingredients to spintronic applications such as spin-to-charge conversion [1]. However, it is not clear what determines α_R. For example, the trend of α_R for M(111) surfaces (M = Cu, Ag, Au) is Au(111) > Cu(111) > Ag(111), but this trend doesn’t coincide with that of atomic SOC strength, that is, the order of atomic number. In this study, we have performed first-principles density functional calculations for typical Rashba systems such as M(111) surfaces, Bi/M surface alloys [2] and oxide interfaces [3], and focused on what dominates α_R in terms of the localization length and Wannier center for Rashba states. We will discuss the correlation between α_R and the localization length or Wannier center of Rashba states.

[1] J. C. Rojas Sánchez et al., Nat. Commun. 4, 2944 (2013).
[2] N. Yamaguchi, H. Kotaka and F. Ishii, J. Cryst. Growth, 468, 688 (2017).
[3] N. Yamaguchi and F. Ishii, to be published in Appl. Phys. Express, arXiv:1709.08335.