Actually, there are a number of well-known atheists, who are dualists. Most well known probably, is David Chalmers who has formulated the issue of the 'hard problem' of consciousness in articles and some well-known films (available on YouTube). Also relevant here is Nagel, whose book 'Mind and Cosmos' got wiped all over the kitchen floor by various critics. But anyway Nagel seems to be a dualist, and is famous for his paper, 'What is it like to be a bat?'.
I think also Bertrand Russell at one point was not a materialist or physicalist. So atheism does not equate with materialism. Many Buddhists are atheists, but would not be described as materialist or naturalists or whatever, since they tend to deny that matter or nature actually exist! Plonkers, eh?