High-resolution photoemission spectroscopy of d,f electron systems at the Hiroshima Synchrotron Radiation Center

摘要

Recently, high energy-resolution and low-temperature photoemission spectroscopies ((DELTA)E = 4.5 approx 20 meV and T = 6 approx 300 K) have been realized successfully on undulator beamlines installed at the compact light source at the Hiroshima Synchrotron Radiation Center. In the case of Kondo semimetal CeNiSn, the temperature dependence of the spectra provides clear evidence of pseudogap formation below the characteristic temperature between 50 and 60 K. Resonant photoemission spectra of the Kondo semiconductor CeRhAs and the Kondo semimetal CeRhSb revealed unusual Ce 4f-derived electronic states. The spectral features of CeRhAs differ considerably from the predictions of a periodic Anderson model, while the features of CeRhSh are well described by the model. The spectra of Y_(1-x)Ca_xTiO_3 (x = 0.39) exhibits a sharp Fermi edge at low temperature, corresponding to the metal-insulator transition at approx 150 K, where the carrier density in the Ti 3d bands plays an important role.