Experimental observation of the Bogoliubov transformation for a Bose-Einstein condensed gas
arXiv:cond-mat/0109205 · doi:10.1103/PhysRevLett.88.060402
Abstract
Phonons with wavevector $q/\hbar$ were optically imprinted into a Bose-Einstein condensate. Their momentum distribution was analyzed using Bragg spectroscopy with a high momentum transfer. The wavefunction of the phonons was shown to be a superposition of +q and -q free particle momentum states, in agreement with the Bogoliubov quasiparticle picture.
4 pages, 3 figures, please take postscript version for the best version of Fig 1