Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 20: Correlated Electrons - Poster Session
TT 20.24: Poster
Mittwoch, 28. März 2007, 14:00–17:45, Poster A
Quantum Critical Spin Dynamics of a Cu(II) S=1/2 antiferromagnetic Heisenberg chain studied by 13C-NMR spectroscopy — •H. Kühne1, J. Litterst1, H.-H. Klauss1, S. Grossjohann2, W. Brenig2, A.P. Reyes3, P.L. Kuhns3, C.P. Landee4, M.M. Turnbull4, H.-J. Grafe5, J. Haase5, and B. Büchner5 — 1Institut für Physik der Kondensierten Materie, TU Braunschweig — 2Institut für Theoretische Physik, TU Braunschweig — 3NHMFL, FSU, Tallahassee, USA — 4DPC, Clark University, Worcester, USA — 5Leibnitz-Institut für Werkstoffforschung, Dresden
The antiferromagnetic S=1/2 Heisenberg chain is a model system for quantum many-body physics. It allows a direct comparison between exact theoretical results and experiment for ground state properties and excitations. Cu(C4H4N2)(NO3)2 (CuPzN) is a very good experimental realization of an unperturbed S=1/2 chain [1,2]. In this compound we study the low energy spin dynamics of a Cu(II) S=1/2 spin chain system by means of NMR. We measured the nuclear spin-lattice relaxation rate of 13C as a function of temperature in a wide external magnetic field range from 2T-22T, with an emphasis on the critical field range around 15T. The experimental data are in very good agreement with Quantum Monte Carlo calculations and clearly show the crossover from quantum critical behavior at low temperatures to diffusive modes at elevated temperatures.[1] P. Hammar et al., PRB. 59, 1008 (1999). [2] M.B. Stone et al., PRL 91, 037205 (2003).