Department of Physics Colloquium

Guest speaker: Bruce D. Gaulin, McMaster University
Thursday, 18 October 2018 - 2:45 pm to 3:45 pm
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Title: Ground State Selection in Quantum Pyrochlore Magnets Abstract: The pyrochlore lattice, a network of corner-sharing tetrahedra, is one of the most pervasive crystalline architectures in nature that supports geometrical frustration. We and others have been interested in a family of rare earth pyrochlore magnets with local XY anisotropy, that can display quantum S=1/2 magnetism on such a lattice. I will discuss up to three such magnets, Yb2Ti2O7, Er2Ti2O7 and Er2Pt2O7. Yb2Ti2O7 has been discussed as a "quantum spin ice" candidate ground state system; Er2Ti2O7 displays a non-colinear Neel state at low temperature, selected by an order-by-disorder mechanism, while Er2Pt2O7 displays a novel "Palmer Chalker" state at low temperatures. I will emphasize neutron scattering studies that we have carried out, and briefly discuss how their ground state selection can be understood in terms of anisotropic exchange on the pyrochlore lattice. Refreshments will be served at 2:15 p.m. (BEFORE the seminar) in room ARC 233