A spin-resolved photoemission study of the iron-based superconductor FeSe

Spin-orbit coupling (SOC) has been recognized to contribute substantially to the electronic properties of iron-based superconductors, yet its interplay with superconductivity and nematic order in these materials remains to be fully understood. In addition, angle-resolved photoemission spectroscopy (ARPES) has suggested that additional symmetries may be spontaneously broken in FeSe single crystals, which combined with strong SOC, would lift spin degeneracy in the band structure. Motivated by this, we have performed spin-resolved ARPES measurements on single crystal FeSe, and we directly observe a spin-polarization in the electronic structure which is antisymmetric with respect to the Gamma-point. Utilizing a laser source with full linear and circular polarization control, our experiment further enables us to distinguish different orbital contributions and unravel the coupled spin-orbital texture. We will evaluate scenarios in which this spin-polarization originates intrinsically from the states in the solid, or alternatively is derived extrinsically from the photoemission process. We expect these findings to provide new insights into the role of SOC and spontaneous symmetry breaking in FeSe.