Well I gave my answer from memory and the name is Oppenheimer, not Oppenhauser. I'm getting old. Robert Oppenheimer is considered the "Father of the Atomic Bomb" He is the person who headed up the Manhattan Project.
J. Robert Oppenheimer - Wikipedia, the free encyclopedia
After re-reading your question are you looking for Einstein? He is famous for his Theory of Relativity. He consulted with Roosevelt early on in the quest for a weapon of mass destruction.
Just as a side note, the bomb during it;s development was referred to as "The Gadget"