Quantitative vectorial spin analysis in ARPES: Bi/Ag(111) and Pb/Ag(111)

TL;DR

This paper introduces a quantitative method for analyzing spin polarization vectors in ARPES, applied to Bi/Ag(111) and Pb/Ag(111) systems with large Rashba splitting, revealing fully spin-polarized surface states with out-of-plane components.

Contribution

It presents a novel two-step fitting routine for vectorial spin analysis in ARPES, enabling precise determination of spin polarization directions and magnitudes for surface states.

Findings

Surface states exhibit large spin splitting.

All surface state bands are 100% spin polarized.

Some states have spin polarization vectors rotating out of the surface plane.

Abstract

The concept of vectorial spin analysis in spin and angle resolved photoemission is illustrated in this report. Two prototypical systems, Bi/Ag(111)(sqrt3 x sqrt3)R30 and Pb/Ag(111)(sqrt3 x sqrt3)R30, which show a large Rashba type spin-orbit splitting, were investigated by means of spin and angle resolved photoemission. The spin polarization vectors of individual bands are determined by a two-step fitting routine. First, the measured intensities are fitted with an appropriate number of suitable peaks to quantify the contributions of the individual bands, then the measured spin polarization curves are fitted by varying for each band the polarization direction and its magnitude. We confirm that the surface states experience a large spin splitting. Moreover, we find that all surface state bands are 100 percent spin polarized, and that for some states spin polarization vectors rotate out of the surface plane.