Quantum physics was only part of his areas of interest. In 1921 he published an article about “diving orbits,” i.e. electrons that should move so elliptically around the nucleus of an atom that they repeatedly end up under the circular orbitals of other electrons. In 1925 he corresponded with Einstein about his new theory of quantum gases. He referred to the dissertation of Louis de Broglie in Paris, which he had reviewed and who had postulated with an original theoretical justification that matter, like light, should have wave properties in addition to particles. This and Einstein’s work on quantum gases opened Schrödinger’s eyes, as he retrospectively told him on April 23, 1926.
During his Christmas vacation in the Swiss Alps, in the Villa Herwig in the 1,800 meter high climatic health resort of Arosa at the foot of the Weisshorn, Schrödinger came up with the decisive idea. “At the moment I am plagued by a new atomic theory. If only I could do more mathematics! I am very optimistic about this matter and hope that if I can only handle it mathematically, it will be very nice,” he wrote on December 27th to the experimental physicist Wilhelm Wien in Munich. The important theorist Arnold Sommerfeld also taught there. Schrödinger informed him, back in Zurich, on January 29, 1926 and asked him for his verdict. “As far as my mathematics is sufficient, everything unfolds in the most beautiful way – and yet it is not a copy of the old quantum rules.”
Over strenuous months, Schrödinger worked out his new approach and immediately applied it to describe or explain known experimental data. In total, in his miracle year of 1926, he published four papers with the unwieldy title “Quantization as an eigenvalue problem” in the renowned Annals of Physics. They were received by editor Wilhelm Vienna on January 27th, February 23rd, May 10th and June 21st; They each appeared in print almost two months later. The same publisher, Johann Ambrosius Barth in Leipzig, also published all four parts with two additional articles as a book in 1927 (delivery began in December 1926).
These works are among the most important in physics, indeed in the entire natural sciences of the 20th century – and also among the most frequently cited. The equation formulated by Schrödinger, for which he was rewarded with the Nobel Prize in Physics in 1933, has shaped quantum theory like no other. Of course, it still gives rise to great mystery and controversy.