Field Induced Continuum Excitation in a 1D Quantum Paramagnet

Tao Hong, Johns Hopkins University

Quantum fluctuation can suppress long-range spin order in magnets even down to the lowest temperature `T=0 K'. The spin system remains in a spin-liquid or quantum paramagnetic state. Coordination polymer magnets are excellent systems in which to explore such quantum magnetism. Here we investigate a possible spin ladder system (2, 3-dimethypyridinium)₂CuBr₄ by inelastic neutron scattering from a powder and a single crystalline sample. In zero field there are long lived triplon excitation above an energy gap <0.35 meV, which propagate only along the crystalline a-direction. Above the critical field H_c1=2.5 Tesla the gap is closed and the low energy magnetic excitations form a continuum.

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Last modified 10-May-2007