We report on the principle and realization of a new trap for excitons -- the
diamond electrostatic trap -- which uses a single electrode to create a
confining potential for excitons. We also create elevated diamond traps which
permit evaporative cooling of the exciton gas. We observe collection of
excitons towards the trap center with increasing exciton density. This effect
is due to screening of disorder in the trap by the excitons. As a result, the
diamond trap behaves as a smooth parabolic potential which realizes a cold and
dense exciton gas at the trap center.Comment: 4 Pages, 5 figure