Organic Superconductivity Studied by using Positron Annihilation and ComptonProfile Spectroscopies

摘要

Organic superconductivity was studied by positron annihilation spectroscopy,positron annihilation lifetime (PAL), and two-dimensional angular correlation of annihilation radiation (2D-ACAR). The positron-electron momentum densities of ET-based organic superconductors were measured at room temperature using the 2D-ACAR method. The folded electron densities were found to be in accord with the Fermi surface predicted by a first-principles method using orthogonalized linear combination of atomic orbitals. Positron lifetimes of ET-based organic superconductors were measured as a function of temperature between 1.5K and 300K. A change of electronic density as indicated from the lifetime results was found at the superconducting transition temperature. It was found to be difficult to obtain a good Compton profile at this stage due to the lack of large crystal of organic superconductors. The obtained positron annihilation experimental results, along with theoretical calculations, could be useful in providing clues to search for new organic superconductors in the future.