Self-fulfilling stereotypes: Have researchers tried inventing new group stereotypes?
The "blue eyes brown eyes exercise" involves a completely arbitrary and invented stereotype.

During part of the exercise, Jane Elliott treated the blue-eyed children as the superior group.
The following day, Elliott reversed the exercise, treating the brown-eyed children as the superior group.
She treated people with the superior-eye-color-of-the-day as highly intelligent and able to learn,
and people with the "inferior" eye color as inherently lazy and stupid.

I hear that, during the exercise, the new stereotype does have a significant effect on the subjects.

Perhaps this exercise by a schoolteacher doesn't really qualify as a "well controlled experiment" performed by a "scientist", but it sounds pretty close to what you were looking for.