Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 72: Low-Dimensional Systems: Poster Session
TT 72.11: Poster
Wednesday, March 18, 2015, 15:00–18:00, Poster B
Temperature dependent optical spectra of magnetic excitations of a 4-leg ladder — •Ignacio Vergara1, Kris Cöster2, Luis Fels1, Martin Valldor1,3, Stefan Wessel4, Kai Phillip 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 is a powerful tool for the study of magnetic excitations with total spin S=0, e.g., bimagnon-plus-phonon absorption. 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, because the phonon takes care of momentum conservation. The line shape of the optical conductivity provides important information on the kinetics and on the interactions of the magnetic excitations.
Through n-leg S=1/2 cuprate ladders, one can explore the dimensional crossover between 1D and 2D systems. The magnetism of n-leg ladders is of particular interest due the possible relevance for high Tc superconductivity. We present temperature-dependent optical conductivity data of the 4-leg ladder La2Cu2O5. We report on a pronounced two-triplon resonance and compare the results with optical spectra of a 2-leg ladder compound and theory (CUT, QMC). Calculations for open and closed boundary conditions give insight on the character of the observed excitations.