4.10.2016

The laureates of the Nobel Prize in Physics 2016 are David J. Thouless, for one half, and F. Duncan M. Haldane with J. Michael Kosterlitz for the second half, for «theoretical discoveries of topological phase transitions and topological phases of matter ».

The ILL is delighted with this choice. Neutrons are at the heart of the experimental investigations of the systems studied by this year's laureates.

In addition Duncan Haldane worked as a post-doc in ILL's theory group. He came to ILL in 1977 at the invitation of Philippe Nozières, after his thesis with Phil Anderson at Cambridge. While at ILL he worked on generalisations of the Anderson impurity models and went on to develop his seminal work on one dimensional quantum liquids and spin chains. His theoretical views also found applications in the physics of stepped surfaces, since steps on a surface are analogous to the trajectories of particles in space-time, if the space is one-dimensional. In examining the relation between exactly soluble one-dimensional models and quantum field theories in two dimensions, he argued for an essential difference between half-integer and integer spin chains related to what are now known as topological terms in quantum field theory. This lead to his prediction of a gap in the excitation spectrum of integer quantum spin chains even without underlying spin anisotropy - an example in condensed matter physics of the phenomenon of dynamical mass generation which is of importance in particle physics.

This "Haldane spin gap" was later confirmed experimentally by inelastic neutron scattering. Duncan's work on low-dimensional quantum physics continued after his four years at ILL and this early work laid the groundwork for notable contributions in the fractional quantum Hall effect and other topological field theories.