Cerium pyrochlores as multipolar spin liquid candidates

Rare earth pyrochlore oxides R₂M₂O₇ have long been thought of as likely candidates to realize three-dimensional quantum spin liquids (QSLs), with highly entangled ground states and fractionalised excitations. Recent experiments have suggested that such a realization may have been achieved in the cerium pyrochlores, Ce₂Sn₂O₇ and Ce₂Zr₂O₇. One reason for the interest in these materials is that the exchange Hamiltonian describing their low energy physics is unusually simple and unusually supportive of QSL ground states. The physics is further enriched by the role of multipolar moments, which allows the existence of octupolar QSLs in which the dominant correlations are those of the cerium octupole moments. In this talk, I will review theoretical and experimental progress in understanding Ce pyrochlores and related materials. I will discuss the ground state phase diagram of the minimal exchange Hamiltonian, and how real materials can be located on this phase diagram by comparing experimental measurements to numerical calculations, leading to the inference that Ce₂Zr₂O₇ realises an exotic π-flux U(1) QSL. This inference nevertheless stops short of an unambiguous demonstration that the QSL state has been realised, and I will discuss how such an experimental demonstration can be achieved.