Magnetic resonance spectroscopy and characterization of magnetic phases   for spinor Bose-Einstein condensates
  The response of spinor Bose-Einstein condensates to dynamical modulation of magnetic fields is discussed with linear response theory. As an experimentally measurable quantity, the energy absorption rate (EAR) is considered, and the response function is found to access quadratic spin correlations which come from the perturbation of the quadratic Zeeman term. By applying our formalism to spin-1 condensates, we demonstrate that the EAR spectrum as a function of the modulation frequency is able to characterize the different magnetically ordered phases. 
Akiyuki Tokuno and Shun Uchino
cond-mat.quant-gas