Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 4: Symposium Superconducting Cuprates

TT 4.5: Fachvortrag

Freitag, 4. März 2005, 16:00–16:30, TU H104

Magnetic Excitations in High-Temperature Superconductors — •Götz S. Uhrig¹, Kai P. Schmidt¹, and Markus Grüninger² — ¹Institut für Theoretische Physik, Universität zu Köln, 50937 Köln — ²II. Physikisches Institut, Universität zu Köln, 50937 Köln

Recently, more and more evidence is emerging that the magnetic excitations in high temperature superconductors have a universal character. The resonance mode at Q_AF and the incommensurate satellites need no longer be regarded as mutually exclusive phenomena pertaining to different families of cuprates. This observation revives the interest in the quantitative theoretical description of the magnetic excitations. One route in the quest for such a theory is to consider charge modulated phases like stripes or tiling patterns which are suggested experimentally by scanning tunnel microscopy and theoretically by phenomenological quantum dimer models.

We present a quantitative description of the universal magnetic excitations which is based on charge stripes where the collective magnetic excitations result from dispersing triplon modes. The anisotropy of the dispersion implies the observed two different energy scales. Very good agreement is obtained for realistic coupling parameters which include a sizable cyclic exchange.

Evidence and counter-evidence for the validity of the model proposed and for possible alternatives is discussed.