Cubic Rashba Effect in the Surface Spin Structure of Rare-Earth Ternary Materials
Dmitry Yu. Usachov, I. A. Nechaev, G. Poelchen, M. Güttler, E. E. Krasovskii, Susanne Schulz, Alexander Generalov, Kristin Kliemt, Alexej Kraiker, C. Krellner, K. Kummer, S. Danzenbächer, C. Laubschat, A. P. Weber, J. Sánchez‐Barriga, Е. В. Чулков, A. F. Santander-Syro, T. Imai, K. Miyamoto, Taichi Okuda, D. V. Vyalikh
Abstract
Spin-orbit interaction and structure inversion asymmetry in combination with magnetic ordering is a promising route to novel materials with highly mobile spin-polarized carriers at the surface. Spin-resolved measurements of the photoemission current from the Si-terminated surface of the antiferromagnet TbRh_{2}Si_{2} and their analysis within an ab initio one-step theory unveil an unusual triple winding of the electron spin along the fourfold-symmetric constant energy contours of the surface states. A two-band k·p model is presented that yields the triple winding as a cubic Rashba effect. The curious in-plane spin-momentum locking is remarkably robust and remains intact across a paramagnetic-antiferromagnetic transition in spite of spin-orbit interaction on Rh atoms being considerably weaker than the out-of-plane exchange field due to the Tb 4f moments.