The Nobel Prize in physics was announced today, and it has surprised a lot of people.

As I wrote in my predictions a couple of days ago, the vast majority of the physics community had assumed that the prize would go to the LIGO team for their detection of gravitational waves earlier this year. Many articles on the Nobel prizes had gone so far as to claim that this was a certainty with no other candidates even being considered. And yet the award committee went a different way.

The 2016 Nobel Prize in Physics has been awarded to David Thouless, and to the team of F. Duncan M. Haldane and J. Michael Kosterlitz for their respective work on topological phase transitions and topological states of matter. And when one reviews their work, it is understandable why the Nobel committee selected them.

In the 1970s scientist were very interested in studying the properties of superconductors and superfluids. A superconductor can transport electricity with no loss, and its ability to repel magnetic fields makes it an ideal candidate for technologies such as high speed trains that float above the tracks. Similarly superfluids, which exist only at very low temperatures, have unique properties that do not appear in ordinary matter and make them useful for testing different theories of matter, and for developing new technologies.

Thouless and Kosterlitz changed the field by using the topology, a branch of mathematics that usually studies surfaces and shapes. They proved that superconductors could exist in thin layers, which at the time was believed by most to be impossible. Perhaps more important, they were able to explain why superconductors suddenly stop superconducting when they reach a specific temperature. It was all due to the topological nature of phase transitions, in which matter changes from one state to another.

Their pioneering work lead to a number of other theoretical models through the 1980s and 1990s that described phase transitions in other materials. In particular, Thouless and Haldane demonstrated how some of the observed properties of superconductors in experiments could be explained as topological effects.

Then in the 2000s and 2010s, a number of experiments were able to cool atoms down sufficiently in a controlled environment, and actually measure some of these topological phase transitions. That seemed to be the proof the Nobel committee needed to recognize that the theoretical work was valid. At present these models are being used to improve our knowledge of superconducting and superfluid phenomena, and a few private companies have even started developing commercial products based on this work. 

For those who are interested, there are two very good, in-depth reviews of this research aimed at a popular science level, and at a professional science level. (I will also be posting a more detailed review of topological phase transitions on my blog when I have some extra time, so watch for that as well).

Congratulations to the winners of the 2016 Nobel Prize in Physics!