Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 49: Correlated Electrons: Low-dimensional Systems - Materials 4
TT 49.1: Vortrag
Freitag, 30. März 2012, 09:30–09:45, H 3005
Crossover from 1D to 2D in the Infrared Absorption of Cuprate Ladder Systems — •Kris Cöster1, Stefan Wessel2, Eva Benckiser3, Michael Voigt4, Markus Grüninger4, and Kai Phillip Schmidt1 — 1Lehrstuhl für Theoretische Physik I , TU Dortmund, 44221 Dortmund, Germany — 2Institut für Theoretische Festkörperphysik, RWTH Aachen University, 52056 Aachen, Germany — 3Max-Planck-Institut für Fest körperforschung, 70569 Stuttgart, Germany — 4II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany
We study the optical spectra of n-leg cuprate ladder systems using infrared absorption and different theoretical tools. The n-leg spin ladders interpolate between the 1D spin chain with fractional excitations and the two-dimensional Heisenberg model on the square lattice relevant for the undoped mother compounds of the high-temperature superconductors. Theoretically, we use perturbative continuous unitary transformations and quantum Monte Carlo simulations to investigate the infrared absorption of n-leg Heisenberg ladders. This joined approach of theory and experiment allows a convincing physical identification of a sharp spectral mode arising from a two-particle bound state dominating the infrared absorption at low energies. This low-energy behaviour of the infrared absorption is a generic feature being present for all studied n-leg ladder systems with n>1.