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O: Oberflächenphysik

O 16: Hauptvortrag Schäfer

O 16.1: Hauptvortrag

Dienstag, 9. März 2004, 10:15–11:00, H36

Electronic Interactions and Phase Transitions at Surfaces and in Low Dimensions — •Jörg Schäfer — Institut für Physik, Universität Augsburg, 86135 Augsburg

Low-dimensional and magnetic systems provide particularly clear-cut cases for the study of modified electron states that result from coupling with elementary excitations. Electronic quasiparticles of enhanced mass have been observed on the energy scale of phonons, and very recently on that of spin waves. Such mechanisms play a role in superconducting pair formation, with spin fluctuations being considered for high-temperature superconductivity.

These interactions together with a nesting condition in the Fermi surface can lead to charge or spin density waves. The phase transition is characterized by the opening of an energy gap and is accompanied by a structural distortion. It can be affected by thermal fluctuations and other metallic states in the system.

Recent progress in photoelectron spectroscopy and synchrotron radiation instrumentation allow to study these effects directly and k-space resolved. Various examples on surfaces, in quasi-one dimensional crystals, and in magnetic materials will be shown.