Max ____ of quantum theory (6)

I believe the answer is:

planck

(Other definitions for planck that I've seen before include "German physicist, initiator of quantum theory, d. 1947" , "German physicist giving name to a constant" , "Max --, German scientist, gave name to a constant" , "Max ---, quantum theorist" .)

I've seen this clue in The Times and The Sunday Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.