Prof Robert McGreevy, Director of ISIS, says, “We are delighted to hear the news of the Nobel prize being awarded to Kosterlitz, Thouless and Haldane – three pioneers in the field of condensed matter physics, whose work underpins a growing area of research at ISIS. Their recognition of the importance of topology and that topological defects interact and participate in phase transitions, allowed huge progress in our understanding how a wide range of materials behave."
The transition of matter to different phases is very familiar to us in our three dimensional world – for example the familiar phases of water from ice to liquid and then to gas. But for a long time the consensus was that when shrinking materials down to one or two dimensions there could be no equivalent phase transitions, even at extremely cold temperatures. Thouless and Kosterlitz were able to show was that this view was incomplete and that it was necessary to consider the topological nature of the materials under investigation. Not only that, Haldane showed that there were also important new quantum phases that require an understanding of topology to describe them.
Prof Sean Langridge, Head of the Diffraction and Materials Division at ISIS, says, “It was particularly appealing in that their theoretical work was universal and could be applied to a wide range of systems: two dimensional superconductors, superfluids and magnetic films. To fully understand such materials requires a precise and delicate probe of matter that can access the low temperatures typically required for matter to manifest their quantum behaviour.”
Neutron scattering, which provided early insights into the nature of magnetic order, was used to find evidence of the behaviour predicted by Kosterlitz and Thouless which is now a cornerstone of our understanding of matter and its transformations. Prof Langridge adds, “This is where facilities like ISIS and its beams of neutrons and muons come into their own by allowing investigators to experimentally access a wide range of such topological quantum matter. For example, the Haldane gap, cited in the Nobel award, was observed using neutron scattering and explored on the MARI instrument here at ISIS.”
While its importance was recognized early on, the work of all three prize winners was sufficiently far ahead of its time that the full ramifications have started to become clear only in the last ten years. The breadth of research at ISIS that contributes to the current rapid progress in this field continues to expand including work on Haldane chains, magnetic quantum Hall analogues and quantum spin liquids to name a few.
As our understanding of condensed matter grows so too does the potential for new applications. Prof Langridge concludes, “It is particularly exciting that such basic research into topological quantum matter is paving the way for future generations of fast, energy efficient devices, and I am delighted to see it recognised by the Nobel committee.”
Dr Andrew Taylor is Director of National Labs at STFC. He says, “It’s great to see the breadth of physics recognised by the Nobel committee, but really exciting to see an area so close to the heart of the work of the Science and Technology Facilities Council. Our facilities played a key role in providing experimental confirmation of the theories, and we continue to provide the unique capabilities and experimental capacity for international researchers inspired by Kosterlitz, Thouless and Haldane to understand these exotic states of matter.”