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College Lecture Series

Pinch points in condensed matter and beyond

Speaker: Prof Steven Bramwell (University College London)
Date: Tuesday 4 February 2020
Time: 13:00
Venue: Queens Buildings N/4.07

Our basic picture of condensed matter involves drawing a distinction between 'order' and 'disorder', as evidenced, respectively, by Bragg peaks and blobs or rings of scattering. However, modern, high resolution X-ray and neutron scattering sources can resolve a third type of scattering: 'pinch points' - near singularities in the structure factor that indicate special type of highly correlated state that is neither entirely ordered, nor entirely disordered. In this talk I will explain how pinch points are in part an illusion and in part an important diagnostic of a very special state. To explain this, I will refer to several types of material and meta-material, including water ice, spin ice, artificial spin ice, ionic solids and models of dipolar liquids, electrolytes and superfluids. I will also point out analogies with general physics.