Early experimental evidence of a topological quantum state: The signature of the Haldane ground state revealed by scattered neutrons
Mechthild Enderle - Institut Laue-Langevin
Michel Kenzelmann - Paul-Scherrer Institut
W.J.L. (Bill) Buyers - Canadian Neutron Beam Centre
The experimental confirmation of the Haldane gap in 1985 by researchers working at Chalk River was a major contribution toward validating the theoretical ideas of Thouless, Haldane, and Kosterlitz, who won the Nobel Prize in Physics in 2016. This article reviews the signatures of Haldane’s predicted topological quantum ground state and their observation in early neutron scattering experiments, which overturned the wisdom of the day.