Yoshikatsu Sugiura's Contribution to the Development of Quantum Physics in Japan

Previous research in the history of physics has led us to believe that Yoshio Nishina (1890-1951) virtually single-handedly imported quantum physics into Japan. However, there are first-hand accounts that Yoshikatsu Sugiura (1895-1960) also played an important role. Sugiura made his name in quantum chemistry with his contribution to the Heitler-London theory of the chemical bond. Yet, historians of physics have paid scant attention to him. This paper brings forward information on Sugiura from his letters, his scientific papers, and his own recollections until ca. 1930. By examining this material, the present paper studies Sugiura's accomplishments in Europe and his contributions to the development of quantum physics in Japan. We conclude that Sugiura was one of the most important physicists when it comes to the arrival of quantum physics in Japan. In addition, we assess why he has been under-appreciated in the history of physics in Japan. Our historical study on Sugiura suggests that, in addition to the position Nishina and his students rightfully occupy, there still are important unexplored aspects in the history of Japanese quantum physics.