Paul Erdős was a mathematician noted for his prolific contributions to the science of mathematics as well as a proclivity for the use of amphetamines. His friend Ronald Graham famously bet him $500 (in the 1970's) that he could not stop taking amphetamine for a month. He successfully completed the challenge, however begrudgingly, saying, "Before, when I looked at a piece of blank paper my mind was filled with ideas. Now all I see is a blank piece of paper."
Erdős resumed his amphetamine use after the month was over, allegedly asserting that the science of mathematics had been set back by a month due to his abstinence. While it is not immediately clear which of his mathematical works were completed under the influence of amphetamines and which were not, it is quite likely that at least some of his work, especially in the last quarter-century of his life, was created under the influence of stimulants.
A mention should also be given to a commonly-related story about Drs. Watson and Crick that they discovered the structure of DNA under the influence of LSD; while although they have been historically credited for the discovery, credit has been more recently given to Dr. Rosalind Franklin, whose unpublished work on DNA structure was evidently shared with Watson and Crick some months before their historic article was published in Nature. Therefore, the story that they first imagined the double-helix structure of DNA molecules while under the influence of the psychedelic must be at least somewhat apocryphal.