Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 13: Correlated Electrons: Low-dimensional Systems - Materials 1
TT 13.2: Vortrag
Dienstag, 26. Februar 2008, 09:45–10:00, H 2053
Highly frustrated S=1/2 spin chains near a quantum critical point — •R. Klingeler1, S.-L. Drechsler1, N. Tristan1, V. Kataev1, F. Kretzschmar1, Y. Arango1, N. Leps1, J. Vavilova1, A. Parameswaran1, H.-H. Klauss2, H. Luetkens3, O. Volkova4, A. Vasiliev4, T. Lorenz5, H. Rakoto6, U. Zeitler7, J. Richter8, and B. Büchner1 — 1Leibniz Institute for Solid State and Materials Research (IFW) Dresden — 2TU Dresden — 3PSI Villingen — 4Moscow State University — 5University of Köln — 6LNCMP Toulouse — 7HMFL Nijmegen — 8University Magdeburg
Frustrated antiferromagnetic quantum spin chains with competing nearest and next-nearest neighbor interactions exhibit a rich physics with unusual ground states. Effects of quantum fluctuations are particularly strong in the vicinity of a quantum critical point where small perturbations such as a weak external magnetic field or the inter-chain coupling strongly affect the physical properties. This situation is realized in the novel S=1/2 spin chain compound Li2ZrCuO4 which is close to a quantum critical point. We report on specific heat, thermal expansion and magnetisation as well as on NMR, ESR and µSR studies which confirm high frustration and strong quantum fluctuations. While inter-chain coupling yields long range antiferromagnetic order at low temperatures our data suggest short range helical/AFM correlations above TN. Upon application of a magnetic field of 9T, however, these correlations are suppressed against ferromagnetic ones. ESR and NMR data confirm the coexistence of quasi-1D behavior and short range AFM correlations up to 80 K ≫ TN ≈ 7 K.