COLLECTIVE EXCITATIONS, METASTABILITY, AND NONLINEAR RESPONSE OF A TRAPPED 2-SPECIES BOSE-EINSTEIN CONDENSATE

We present a new theoretical treatment of the collective excitation sp ectrum of a two-species Bose-Einstein condensate confined in a magneti c trap, We show that the interspecies interaction significantly modifi es th excitation spectrum and gives rise to a rich set of new phenomen a. We identify a novel metastable stare of the double condensate and s how that under external perturbation there can be a macroscopic quantu m transition between this metastable state and the true ground state o f the double condensate system. [S0031-9007(97)05175-2].