Field-tuned transition of a U(1) quantum spin ice in Ce₂Zr₂O₇ - emergent photon suppression and spinon reorganization

We report a field-tuned reconstruction of the low-energy spectrum in the π-flux U(1) quantum spin ice Ce₂Zr₂O₇ under B ‖ [111]. Using a same-temperature high-field background protocol on TOF mapping, we cleanly isolate the magnetic quasi-elastic response that is otherwise buried under the NSF elastic/incoherent/holder background, consistent with previous polarization-analyzed TAS. At zero fields the spectrum shows the hallmark quasi-elastic upturn, consistent with the emergent photon of lattice U(1) gauge theory. With increasing field, this quasi-elastic weight is suppressed and collapses, while the spinon continuum at finite energy reorganizes rather than vanishing—demonstrating distinct field responses of photon and spinons.