The Landscape Problem of Frustrated Magnetism: Has Compelling Experimental Evidence for Order-by-Disorder at Last Been Found?

Department Colloquia

Speaker: Michel Gingras Department of Physics & Astronomy, University of Waterloo
Date & Time: January 23, 2014 16:00 - 17:00
Location: UBC, Hennings 201
Local Contact: Marcel Franz
Intended Audience: Undergraduate

In some magnetic systems, known as frustrated magnets, the lattice geometry or the competition between different spin-spin interactions can lead to a sub-exponentially large number of accidentally degenerate classical ground states, or false vacuua, and thus a sort of landscape problem for condensed matter physicists. Order-by-disorder (OdD) is a concept of central importance in the field of frustrated magnetism. Saddled with large accidental degeneracies, a subset of states, those that support the largest quantum and/or thermal fluctuations, may be selected to form true long-range order. ObD hasbeen discussed extensively on the theoretical front for over 30 years and proposed to be at play in a number of experimental settings. Unfortunately, convincing demonstrations of OBD in real materials have remained scarce. In this talk, I will review the phenomena of thermal and quantum of order-by-disorder and discuss how recent work may have evinced compelling evidence for ObD in some frustrated XY pyrochlore antiferromagnetic mateirals.