Quantum Spin Ice in magnetic field: Experimentally Tunable QED, Kasteleyn transition and flux liquid

Recent investigations of the dipolar-octupolar pyrochlores Ce₂Zr₂O₇ and Ce₂Hf₂O₇ have provided tanatilising glimpses of quantum spin ice physics. Nonetheless, firmer evidence is needed to confirm the presence of a QSL ground state. In this work, we consider the experimentally reasonable proposition of applying external magnetic field to quantum spin ice. We show that applied magnetic field generally promotes classical ordering along β-chains, in effect mimicing strain effects known from previous studies of classical spin ice to cause a highly exotic 3D Kasteleyn transition (Jaubert et al. 2008, PRL 100(6), 067207). At zero temperature and weak field, the effective Ising term competes energetically with quantum ring exchange, in a fascinating and experimentally realisable example of the theoretical quantum Kasteleyn transition of the diamond lattice dimer model (Powell 2022, PRB 105, 064413). Finally, in the special case of [111] field direction, we see that the applied field can induce a novel 'frustrated flux' phase in the quantum spin liquid that is stable up to very large magnetic fields. Our results offer a wide range of concrete predictions applicable to current candidate materials, which will be useful to future experimental investigations.