John J. Hopfield is a physicist known for his coefficients in solid-state physics, whereby light and matter strongly couple to form polaritons,[1] and for his neural networks, when he suddenly changed field.[2]
He was the Ph. D of A. Overhauser, who let him work independently on his thesis problem (the polariton):
The polariton, a new solid state physics particle, was invented to resolve the paradoxical situation. The single paper written from the 1958 thesis is still highly cited (as is the single author) thanks to the existence of lasers, the polariton condensate, and modern photonics. Thank you, Al. I have done my best to repay you through similarly nurturing another generation of independent students.—In Ref. [3].
He wrote a great essay on what Physics is and the evolution of solid-state physics into various subbranches.[3].