Atomic Physics Workshop

Small electronic systems with electron-phonon interaction

A cluster of metallic atoms is considered, where electrons can tunnel between the atoms. Then the effect of electronic correlations on the tunneling properties is studied. Electronic degrees freedom can also couple to atomic vibrational modes, which leads to an effective electron-phonon coupling. Two cases are discussed here, one in which an electron has only a single state at each atom (Holstein model) and another one in which each atom provides two orbitals for an electron (Jahn-Teller model). In both cases the interplay of electronic correlations and the electron-phonon coupling are studied. For this purpose a recursive projection method for the underlying Hilbertspace is introduced that provides a systematic approach to low-energy states and increasingly higher excitations. The method generates a sequence of effective Hamiltonians which can be linked to specific physical phenomena.