Observation of Spin-Split Electronic States in Solids by Energy-, Angle-, and Spin-Resolved Photoemission

The combination of high energy and angle resolution (100 meV, ±3°) with spin analysis in photoemission spectroscopy is shown to allow the direct observation of magnetically spin-split electronic states. This is demonstrated for normal emission from Ni(110) with polarized Ne i radiation ($h\nu =16.85\mathrm{}$ eV). It is found that ${\Delta }_{\mathrm{ex}}=0.18\mathrm{}$ eV for the exchange splitting of the $S_4$ band at the $X$ point in good agreement with a band-structure and photoemission calculation that considers the self-energy correction explicitly.