The case for a U(1)_π Quantum Spin Liquid Ground State in the Dipole-Octupole Pyrochlore Ce₂Zr₂O₇

The Ce³⁺ pseudospin-½ degrees of freedom in the pyrochlore magnet Ce₂Zr₂O₇ are known to possess dipole-octupole character, making it a candidate for novel quantum spin liquid ground states at low temperatures. We’ve measured the heat capacity of Ce₂Zr₂O₇ and fit the result to a quantum numerical linked cluster (NLC) calculation that allows estimates for the terms in the near-neighbour XYZ Hamiltonian expected for such dipole-octupole pyrochlore systems.  Fits of the same theory to the temperature dependence of the magnetic susceptibility and unpolarized neutron scattering complement this analysis to produce robust estimates of the near-neighbour exchange parameters.  A comparison between the resulting best fit NLC calculation and new polarized neutron diffraction results shows agreement, as well as discrepancies which are attributed to interactions beyond near-neighbours, such as zone-boundary diffuse scattering in the non-spin flip channel. We conclude that Ce₂Zr₂O₇ realizes a U(1)_π quantum spin liquid state at low temperatures, and one that resides near the boundary between dipolar and octupolar character.