Exploring spin-polarization in Bi-based high-Tc cuprates

The role of spin-orbit interaction has been recently reconsidered in high-T-c cuprates, stimulated by the recent experimental observations of spin-polarized electronic states. However, due to the complexity of the spin texture reported, the origin of the spin polarization in high-T-c cuprates remains unclear. Here, we present the spin-and angle-resolved photoemission spectroscopy (ARPES) data on the facing momentum points that are symmetric with respect to the G point, to ensure the intrinsic spin nature related to the initial state. We consistently found the very weak spin polarization only along the nodal direction, with no indication of spin-splitting of the band. Our findings thus call for a revision of the simple application of the spin-orbit interaction, which has been treated within the standard framework of the Rashba interaction in high-T-c cuprates.