Scientific Background on the Nobel Prize in Physics 2016

1 Introduction
In 1972 J. Michael Kosterlitz and David J. Thouless identified a completely
new type of phase transition in two-dimensional systems where topological
defects play a crucial role [35, 36]. Their theory applied to certain kinds of
magnets and to superconducting and superfluid films, and has also been very important for understanding the quantum theory of one-dimensional systems at very low temperatures.

Source: advanced-physicsprize2016.pdf