Peter C.W. Holdsworth - Emergence: from spins to charges
Channel: Institut des Hautes Études Scientifiques (IHÉS)
Date: 2021-06-17

Emergence is a major buzz word of our times. My working definition, which gives plenty of room for manoeuvre is: the appearance of many body phenomena of higher symmetry than that of the Hamiltonian and degrees of freedom at the microscopic level.


In this colloquium I will discuss a topical example - the frustrated magnetic material, spin ice. Here, to an excellent approximation a classical field theoretic description with continuous U(1) symmetry emerges from Ising like degrees of freedom. The associated quasi-particles appear to be freely moving magnetic charge - magnetic monopoles - and the system behaves as a magnetic Coulomb fluid in the grand canonical ensemble with intrinsic topological properties. With the addition of quantum fluctuations the emergent magneto-statics develops further into a complete analogue of quantum electrodynamics. I will aliment this discussion with experimental results from a wide range of systems.


Organisé par Vasily Pestun & Slava Rychko