Development of highly efficient and stable spin polarimeter for an undulator-based angle-resolved photoemission spectroscopy beamline

Abstract

Highly efficient and reliable spin- and angle-resolved photoelectron spectroscopy (spin-ARPES) has been developed at the 4A2 beamline of Pohang Light Source II. The spin polarimeters based on exchange scattering by a ferromagnetic target were integrated into a state-of-the-art hemispherical electron analyzer, enabling us to obtain the electronic band structure with a three-dimensional spin polarization character. The figure of merit (FOM) of the spin polarimeter was proven to be higher than those of conventional Mott detectors by two orders. The spin-dependent electron reflectivity spectra of in situ grown ferromagnetic targets were obtained by the use of a kinetic energy control lens and they are utilized to optimize and stabilize the spin detection asymmetry. The overall performance was demonstrated by measuring the spin-ARPES spectra of the Dirac cone of \(\hbox {Bi}_2 \hbox {Se}_3\).