[show abstract][hide abstract] ABSTRACT: We used low-temperature ultrahigh-resolution (360 microeV) photoemission spectroscopy with a laser as a photon source (Laser-PES) to study the superconducting (SC) gap of an f-electron superconductor CeRu2. The unique combination of the large escape depth expected from the known universal behavior and extremely high-energy resolution has enabled us to directly measure the bulk SC gap of an f-electron superconductor for the first time. The present study provides direct evidence for an anisotropic SC gap in CeRu2, and also demonstrates the potential of Laser-PES in investigating unconventional superconductivity realized in correlated d- and f-electron superconductors.
[show abstract][hide abstract] ABSTRACT: We have developed an ultrahigh-resolution photoemission system using a quasi continuous wave (quasi-CW) VUV laser. The photon energy of the VUV laser is 6.994eV. It has a line width of 260μeV and a repetition rate of 80MHz. The photon energy of this laser is the highest for a quasi-CW laser. Using a quasi-CW laser removes the space charge effect and hence does not degrade the energy resolution. For the electron analyser, we use the newly designed ultrahigh-resolution photoelectron analyser GAMMADATA-SCIENTA R4000. The analyser resolution is about 250μeV with a wide collecting angle of about 38°. The total energy resolution of this system is measured to be 360μeV for the Fermi edge of gold. Using this system, we have measured several low transition temperature superconductors and succeeded to observe the bulk superconducting state of these materials.
Journal of Electron Spectroscopy and Related Phenomena - J ELECTRON SPECTROSC RELAT PH. 01/2005; 144:953-956.