We discuss a method to create two-dimensional 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 novel 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.Comment: 16 pages, 10 figure