バルク敏感角度分解光電子分光による固体 3 次元電子構造とフェルミ面の観測

High-resolution and high-excitation energy photoemission spectroscopy has an advantage in probing the bulk electronic states in solids whereas the surface electronic states deviated from the bulk states are strongly reflected in low-excitation energy photoemission spectra which have so far extensively measured for many materials. We have succeeded in realization of the high-energy bulk-sensitive angle-resolved photoemission in order to probe the three-dimensional electronic structures and the Fermi surfaces. After introducing the angle-integrated photoemission spectra of 3d1-electron system Sr1-xCaxVO3 as an example for the bulk (surface) sensitivity of the high-(low-)energy photoemission, we show the recently obtained results of high-energy angle-resolved photoemission for strongly correlated electron systems such as Sr2RuO4 and ferromagnet CeRu2Ge2 in the paramagnetic phase, revealing their bulk Fermi surfaces. It is found that the Fermi surfaces of CeRu2Ge2 in the paramagnetic phase are substantially deviated from those in the ferromagnetic phase. Although our results for CeRu2Ge2 are roughly explained by the band-structure calculation for LaRu2Ge2, a few qualitative discrepancies are seen.