Otto Stern is the second most nominated person for a Nobel Prize behind a German theoretical physicist who pioneered developments in what?
Arnold Sommerfeld Arnold Johannes Wilhelm Sommerfeld, {'1': ", '2': ", '3': 'ForMemRS', '4': "} (] ; 5 December 1868 – 26 April 1951) was a German theoretical physicist who pioneered developments in atomic and quantum physics, and also educated and mentored a large number of students for the new era of theoretical physics. He served as PhD supervisor for many Nobel Prize winners in physics and chemistry (only J. J. Thomson's record of mentorship is comparable to his).
Walter Gerlach Walther Gerlach (1 August 1889 – 10 August 1979) was a German physicist who co-discovered spin quantization in a magnetic field, the Stern–Gerlach effect.