The magnetic excitation spectrum in the two-dimensional (2D) S = 1/2 Heisenberg antiferromagnet copper deuteroformate tetradeuterate has been measured for temperatures up to T similar to J/2, where J = 6.31 +/- 0.02 meV is the 2D exchange coupling. For T << J, a dispersion of the zone boundary energy is observed, which is attributed to a wave vector dependent quantum renormalization. At higher temperatures, spin-wavelike excitations persist, but are found to broaden and soften. By combining our data with numerical calculations, and with existing theoretical work, a consistent description of the behavior of the model system is found over the whole temperature interval investigated.
|Journal||Physical Review Letters|
|Pages (from-to)||037202.1-037202.4 ( and reply to comment (Peter Kopietz and Ivan Spremo) Phys. Rev. Lett. 2002, v. 89, art. no. 079702)|
|Publication status||Published - 2001|