Quantum Phase Transition in Quantum Spin Liquid Candidate Ce2Zr2O7

The interplay between symmetry and topology is a major theme of condensed matter physics. Nontrivial realization of symmetries has led to various states with different macroscopic quantum coherence. Among them, quantum spin liquid (QSL) state, which has no conventional order parameter associated with broken symmetry, can emerge in insulators containing localized spin degrees of freedom. Practically, QSL states are characterized by a fractionalized spin excitation that can be revealed by inelastic neutron scattering. A key consequence of QSL scenario is the presence of a quantum phase transition in the applied magnetic field. Such a transition is required to remove the fractionalized excitation from the spectrum. At a low field and temperature, the QSL state may support exotic excitations like magnetic monopoles, while in a higher field, the ground state is a spin-polarized ferromagnet.