High-T_c superconductor studied with synchrotron radiation

Synchrotron radiation studies of the electronic structure of high-T_c superconductors are presented. High-energy spectroscopies such as photoemission and X-ray absorption using synchrotron radiation have succeeded in revealing the electronic structure of high-T_c superconductors. The experimental results show that, although the electronic structure is largely modified by a strong electron correlation effect, the electronic states near the Fermi level are described in terms of the Fermi liquid. This supports a Fermi-liquid approach based on the BCS theory for understanding the high-T_c mechanism.