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).
Heinrich Welker Heinrich Johann Welker (September 9, 1912 in Ingolstadt – December 25, 1981 in Erlangen) was a German theoretical and applied physicist who invented the "transistron", a transistor made at Westinghouse independently of the first successful transistor made at Bell Laboratories. He did fundamental work in III-V compound semiconductors, and paved the way for microwave semiconductor elements and laser diodes.