Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 17: Symposium Quantum Magnetism in Molecule-based Materials

TT 17.1: Hauptvortrag

Montag, 7. März 2005, 10:15–10:50, TU H104

From Spin to Quantum Order in Coordination Polymer Magnets — •Collin Broholm — Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA

Coordination polymer magnets feature transition metals such as Cu and Ni on a range of different lattices and offer opportunities for exploring qualitatively different cooperative phases of quantum many body systems. This talk will present an overview of neutron scattering experiments that have been performed to understand spin dynamics in systems ranging from spin-chains (copper pyrazine dinitrate, CuCl₂· 2dimethylsulfoxide, NENP, and NDMAP) through a spin-ladder (Cu(Quinoxaline)Br₂) to frustrated two and three dimensional systems (PHCC and CuHpCl). While the isolated spin-1/2 chain systems are quantum critical and can develop spin order due to weak inter-chain interactions at sufficiently low temperatures, cooperative singlet ground states are in fact more common in these low symmetry antiferromagnetic spin systems. The qualitatively different excitations spectra of gapless and gap-full systems will be described as well as their different responses to applied magnetic fields.