Living on the edge: multiple phase competition and topological order in pyrochlore oxides

Pyrochlore oxides, A2B2O7, are one of nature's best tricks - ubiquitous minerals, capable of incorporating an extremely wide range of metal cations. Over the past decade these materials have risen to prominence in the community studying frustrated magnetism, for their ability to instantiate so many different novel, and topological phases of matter. Best known among these is spin ice, celebrated for its magnetic monopole excitations, but small changes in chemistry can lead to a wide range of other exotic phonomena, including both classical and quantum spin liquids.

In this talk, we explore one particular avenue in this lively field, namely the multiple-phase competition which occurs in magnetic oxides with strong spin-orbit coupling. Considering Yb2Ti2O7, Er2Ti2O7 and Er2Sn2O7 as examples, we show how the seemingly diverse physics of these systems can be understood through a single unifying principle, namely the interplay between different competing forms of order [1]. We also explore how this conceptual framework can be used to "design" new forms of spin liquid, including phases which realise fracton topological order.

Finally, we pose the question, could different modes of growth give us access to pyrochlore oxides with even more exotic, or controlable, properties ?

[1] Han Yan, Owen Benton, L.D.C. Jaubert and Nic Shannon, Phys. Rev. B 95, 094422 (2017)