During these fellowships, Schopper worked on nuclear physics and contributed substantially to the evidence of parity violation in weak interactions. He measured the circular polarization of gamma rays following a beta decay, thought unfeasible by Lee and Yang, and showed in the same experiment that the helicities of neutrino and antineutrino are opposite. Later, he was involved in an experiment to test time reversal symmetry. In 1956, he followed Fleischmann to the University of Erlangen where he continued to do research in optics and solid-state physics, with emphasis on thin metal layers, which he had started at Hamburg. Also he developed, along with Clausnitzer, the first source of polarised protons. In 1957 he became Privatdozent at the University of Erlangen.