Emergent photons and fractionalized excitations in a quantum spin liquid

Abstract

A quantum spin liquid (QSL) arises from a highly entangled superposition of many degenerate classical ground states in a frustrated magnet, and is characterized by emergent gauge fields and deconfined fractionalized excitations (spinons). Because such a novel phase of matter is relevant to high-transition-temperature superconductivity and quantum computation, the microscopic understanding of QSL states is a long-sought goal in condensed matter physics. The 3D pyrochlore lattice of corner-sharing tetrahedra can host a QSL with U(1) gauge fields called quantum spin ice (QSI), which is a quantum (with effective $S=1/2$) analog of the classical (with large effective moment) spin ice. A key difference between QSI and classical spin ice is the predicted presence of the linearly dispersing collective excitations near zero energy, dubbed the "photons", arising from emergent quantum electrodynamics, in addition to the spinons at higher energies. Recently, 3D pyrochlore systems Ce2M2O7 (M = Sn, Zr, Hf) have been suggested as effective $S=1/2$ QSI candidates, but there has been no evidence of quasielastic magnetic scattering signals from photons, a key signature for a QSI. Here, we use polarized neutron scattering experiments on single crystals of Ce2Zr2O7 to conclusively demonstrate the presence of magnetic excitations near zero energy at 50 mK in addition to signatures of spinons at higher energies. By comparing the energy (E), wave vector (Q), and polarization dependence of the magnetic excitations with theoretical calculations, we conclude that Ce2Zr2O7 is the first example of a dipolar-octupolar $\pi$ flux QSI with dominant dipolar Ising interactions, therefore identifying a microscopic Hamiltonian responsible for a QSL.

References in corpus (52)

• Fault-tolerant quantum computation by anyons
• Anyons in an exactly solved model and beyond
• Quantum Spin Liquids
• Spin Ice State in Frustrated Magnetic Pyrochlore Materials
• Quantum Spin Liquid States
• Magnetic Pyrochlore Oxides
• Fractionalized excitations in the spin liquid state of a kagomé lattice antiferromagnet
• Quantum Spin Liquids
• Kitaev quantum spin liquid - concept and materialization
• Antiferromagnetic order and spin dynamics in iron-based superconductors
• Pyrochlore Photons: The U(1) Spin Liquid in a S=1/2 Three-Dimensional Frustrated Magnet
• Herbertsmithite and the Search for the Quantum Spin Liquid
• Quantum Spin Ice: A Search for Gapless Quantum Spin Liquids in Pyrochlore Magnets
• Continuous excitations of the triangular-lattice quantum spin liquid YbMgGaO4
• Evidence for a spinon Fermi surface in a triangular lattice quantum spin liquid candidate
• Coulombic Quantum Liquids in Spin-1/2 Pyrochlores
• Seeing the light : experimental signatures of emergent electromagnetism in a quantum spin ice
• Generic quantum spin ice
• Experimental signatures of a three-dimensional quantum spin liquid in effective spin-1/2 Ce2Zr2O7 pyrochlore
• Quantum spin ices and topological phases from dipolar-octupolar doublets on the pyrochlore lattice
• Quantum Ice : a quantum Monte Carlo study
• Physical realization of a quantum spin liquid based on a novel frustration mechanism
• Unusual liquid state of hard-core bosons on the pyrochlore lattice
• Quantum Spin Ice Dynamics in the Dipole-Octupole Pyrochlore Magnet Ce${}_2$Zr${}_2$O${}_7$
• Disordered Route to the Coulomb Quantum Spin Liquid: Random Transverse Fields on Spin Ice in Pr${}_2$Zr${}_2$O${}_7$
• A quantum liquid of magnetic octupoles on the pyrochlore lattice
• Spinon Fermi surface spin liquid in a triangular lattice antiferromagnet NaYbSe${}_2$
• Quasiparticle Breakdown and Spin Hamiltonian of the Frustrated Quantum Pyrochlore Yb${}_2$Ti${}_2$O${}_7$ in Magnetic Field
• Experimental signatures of emergent quantum electrodynamics in Pr${}_2$Hf${}_2$O${}_7$
• Witnessing entanglement in quantum magnets using neutron scattering
• Witnessing quantum criticality and entanglement in the triangular antiferromagnet KYbSe${}_2$
• Symmetry Enriched U(1) Topological Orders for Dipole-Octupole Doublets on a Pyrochlore Lattice
• Experimental Insights into Ground State Selection of Quantum XY Pyrochlores
• Numerical evidence of quantum melting of spin ice: quantum-classical crossover
• Dynamics of Topological Excitations in a Model Quantum Spin Ice
• Sleuthing out exotic quantum spin liquidity in the pyrochlore magnet Ce${}_2$Zr${}_2$O${}_7$
• Multiphase Magnetism in Yb2Ti2O7
• Complete field-induced spectral response of the spin-1/2 triangular-lattice antiferromagnet CsYbSe${}_2$
• Field-Induced Spin Excitations in the Spin-1/2 Triangular-Lattice Antiferromagnet CsYbSe${}_2$
• The Spectral Periodicity of Spinon Continuum in Quantum Spin Ice
• Spectral function of the $J_1-J_2$ Heisenberg model on the triangular lattice
• Ground state phase diagram of dipolar-octupolar pyrochlores
• Magnetic field effects in an octupolar quantum spin liquid candidate
• Crystal-field states and defect levels in candidate quantum spin ice Ce${}_2$Hf${}_2$O${}_7$
• Uncovering footprints of dipolar-octupolar quantum spin ice from neutron scattering signatures
• Symmetry fractionalization in the gauge mean-field theory of quantum spin ice
• Dipolar spin ice regime proximate to an all-in-all-out Néel ground state in the dipolar-octupolar pyrochlore Ce${}_2$Sn${}_2$O${}_7$
• Quantum Spin Ice Response to a Magnetic Field in the Dipole-Octupole Pyrochlore Ce${}_2$Zr${}_2$O${}_7$
• Spectroscopic signatures of fractionalization in octupolar quantum spin ice
• In-plane uniaxial pressure-induced out-of-plane antiferromagnetic moment and critical fluctuations in BaFe${}_2$As${}_2$
• $\mu$SR Study of the Dipole-Octupole Quantum Spin Ice Candidate Ce${}_2$Zr${}_2$O${}_7$
• Dipolar-octupolar correlations and hierarchy of exchange interactions in Ce${}_2$Hf${}_2$O${}_7$

Cited by in corpus (9)

• Kitaev Quantum Spin Liquids
• Dipolar-octupolar correlations and hierarchy of exchange interactions in Ce${}_2$Hf${}_2$O${}_7$
• Two-Peak Heat Capacity Accounts for $R\ln (2)$ Entropy and Ground State Access in the Dipole-Octupole Pyrochlore Ce${}_2$Hf${}_2$O${}_7$
• Spinon band flattening by its emergent gauge field in quantum kagome ice
• Influence of controlled disorder on the dipolar spin ice state of Ho-based pyrochlores
• Towards a global phase diagram of Ce-based dipolar-octupolar pyrochlore magnets under magnetic fields
• Hearing the light: stray-field noise from the emergent photon in quantum spin ice
• Classification and correlation signatures of chiral spin liquids on the pyrochlore lattice
• Mapping the Phase Diagram of a Frustrated Magnet: Degeneracies, Flat Bands, and Canting Cycles on the Pyrochlore Lattice