Phys. Rev. Lett. 84, 4465–4468 (2000)Triplet Waves in a Quantum Spin LiquidReceived 13 August 1999; published in the issue dated 8 May 2000 We report a neutron scattering study of the spin- 1/2 alternating bond antiferromagnet Cu(NO3)2̇2.5D2O for 0.06<kBT/J1<1.5. For kBT/J1≪1 the excitation spectrum is dominated by a coherent singlet-triplet mode centered at J1 = 0.442(2)meV with sinusoidal dispersion and a bandwidth of J2 = 0.106(2)meV. A complete description of the zero temperature contribution to the scattering function from this mode is provided by the single mode approximation. At finite temperatures we observe exponentially activated band narrowing and damping. The relaxation rate is thermally activated and wave vector dependent with the periodicity of the reciprocal lattice. © 2000 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.84.4465
DOI:
10.1103/PhysRevLett.84.4465
PACS:
75.10.Jm, 75.40.Gb, 75.50.Ee, 78.70.Nx
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