Atom trapping and two-dimensional Bose-Einstein condensates in field-induced adiabatic potentials

We discuss a method to create two-dimensional (2D) traps as well as atomic shell, or bubble, states for a Bose-Einstein condensate initially prepared in a conventional magnetic trap. The scheme relies on the use of time-dependent, radio-frequency-induced adiabatic potentials. These are shown to form a versatile and robust tool to generate interesting trapping potentials. Our shell states take the form of thin, highly stable matter-wave bubbles and can serve as stepping stones to prepare atoms in highly excited trap eigenstates or to study "collapse and revival phenomena." Their creation requires gravitational effects to be compensated by applying additional optical dipole potentials. However, in our scheme gravitation can also be exploited to provide a route to two-dimensional atom trapping. We demonstrate the loading process for such a trap and examine experimental conditions under which a 2D condensate may be prepared.