{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"6fbcda893e359a85cd751c5e0b9596e047f68194dcf51292874406817f410cc4","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["692e84275354594b030e926ee9b76c7f88ecf4490783f075252d14127adb8d67","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"586db30901bd05606c884dc8951757bb0744df2b44c8747823bc2553dc948d71","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"cm.spin-ice.emergent-photon-evidence","kind":"phenomenon","literature_status":"partially-resolved","n":"2","parents":[],"plain":"Quantum spin ice should host three kinds of emergent particles: photons, electric-like spinons and magnetic monopoles. Cerium pyrochlores such as $\\mathrm{Ce_2Zr_2O_7}$ show signs of these, but alternative explanations are not fully excluded.","posed_since":"2004","precise":"In $\\mathrm{Ce_2Zr_2O_7}$, $\\mathrm{Ce_2Sn_2O_7}$ and $\\mathrm{Ce_2Hf_2O_7}$ (dipolar-octupolar doublets), establish the $\\mathrm{U}(1)$ quantum spin liquid through its distinct signatures: a gapless linearly dispersing transverse photon ($C \\sim T^{3}$ well below the photon bandwidth), a spinon continuum, and their predicted spectral weights. An answer is a fit of thermodynamic and neutron data by quantum spin ice theory with independently fixed exchange parameters that excludes classical or disorder-driven alternatives.","problem_ref":"692e84275354594b030e926ee9b76c7f88ecf4490783f075252d14127adb8d67","references":"","settled_by":"Polarized neutron scattering below $0.05\\,\\mathrm{K}$ resolving the low-energy photon mode and heat capacity showing the $T^3$ term, both matched to quantum Monte Carlo of the fitted XYZ model.","status_note":"Gao et al. (Nature Physics 2025) reported neutron and thermodynamic evidence for emergent photons and spinons in $\\mathrm{Ce_2Zr_2O_7}$, interpreted as a pi-flux quantum spin ice.","title":"Has emergent quantum electrodynamics been observed in a quantum spin 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