Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 23: Low-Dimensional Systems: Other Materials
TT 23.4: Vortrag
Montag, 31. März 2014, 17:30–17:45, BEY 81
Magnetic excitation spectra of the 4-leg ladder La2Cu2O5 — •Ignacio Vergara1, Kris Cöster2, Luis Fels1, Martin Valldor1,3, Stefan Wessel4, Kai Philip Schimdt2, and Markus Grüninger1 — 1II. Physicalisches Institut, Universität zu Köln — 2Lehrstuhl für Theoretische Physik I, Technische Universität Dortmund — 3Max-Planck Institute for Chemical Physics of Solids, Dresden, Germany — 4Institut für Theoretische Festkörperphysik, JARA-FIT and JARA-HPC, RWTH Aachen University
In low-dimensional spin-1/2 cuprates, optical spectroscopy has been established as a powerful tool for the study of magnetic excitations with total S=0. The simultaneous excitation of a symmetry-breaking phonon allows us to study the magnetic excitations at high energies (∼ 0.1 - 1 eV) throughout the entire Brillouin zone, since the phonon ensures momentum conservation. The line shape of the optical conductivity provides important information on the kinetics and on the interactions of the magnetic excitations.
The magnetism of n-leg S=1/2 cuprate ladders is particularly interesting due to the dimensional crossover between 1D and 2D and the possible relevance for high Tc superconductivity. We present optical conductivity data of the 4-leg ladder La2Cu2O5 for polarization of the electric field parallel to the legs and to the rungs, respectively. Comparison with theory (CUT, QMC) and with the results for a 2-leg ladder suggests the existence of two-triplon bound states below the continuum also for n=4.