Part 2*

Quantum spin ice is a three-dimensional quantum spin liquid with an emergent compact U(1) gauge structure that provides a lattice realization of quantum electrodynamics. It supports gapless photon-like modes as well as electric and magnetic monopoles of the emergent gauge theory, commonly referred to as spinons and visons, respectively. There is increasing experimental support for the claim that the dipolar-octupolar compound Ce₂Zr₂O₇ is a material realization of quantum spin ice. The lowest lying doublet of the magnetically active Ce³⁺ ions forming a pyrochlore lattice can be described by pseudospin-1/2 with two components that transform as dipoles and one as an octupolar moment. We theoretically analyze new polarized neutron scattering measurements on Ce₂Zr₂O₇ with Gaussian quantum electrodynamics and gauge mean-field theory. Our modeling allows for a critical examination of competing scenarios for the microscopic interactions and provides evidence for the presence of emergent fractional excitations. Our work lends further support to the identification of Ce₂Zr₂O₇ as a long-sought-after experimental realization of a three-dimensional quantum spin liquid.