Fractionalized charge excitations in a spin liquid on partially-filled pyrochlore lattice

Abstract

We study the Mott transition from a metal to cluster Mott insulators in the 1/4- and 1/8-filled pyrochlore lattice systems. It is shown that such Mott transitions can arise due to charge localization in clusters or in tetrahedron units, driven by the nearest-neighbor repulsive interaction. The resulting cluster Mott insulator is a quantum spin liquid with a spinon Fermi surface, but at the same time a novel fractionalized charge liquid with charge excitations carrying half the electron charge. There exist two emergent U(1) gauge fields or "photons" that mediate interactions between spinons and charge excitations, and between fractionalized charge excitations themselves, respectively. In particular, it is suggested that the emergent photons associated with the fractionalized charge excitations can be measured in X-ray scattering experiments. Various other experimental signatures of the exotic cluster Mott insulator are discussed in light of candidate materials with partially-filled bands on the pyrochlore lattice.

Published version

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• Quantum spin ice on the breathing pyrochlore lattice
• Dirac's "magnetic monopole" in pyrochlore ice U(1) spin liquids: Spectrum and classification
• Dielectric catastrophe at the Mott and Wigner transitions in a moiré superlattice
• Emergent orbitals in the cluster Mott insulator on a breathing Kagome lattice
• Competing phases and topological excitations of spin-one pyrochlore antiferromagnets
• Multiflavor Mott insulators in quantum materials and ultracold atoms
• Coulomb liquid phases of bosonic cluster Mott insulators on a pyrochlore lattice
• LiZn${}_2$V${}_3$O${}_8$: A new geometrically frustrated cluster spin-glass
• Monopole holes in a partially ordered spin liquid
• Molecular Mott state in the deficient spinel GaV${}_4$S${}_8$
• Metal-Insulator Transition with Charge Fractionalization
• Extended Coulomb liquid of paired hardcore boson model on a pyrochlore lattice
• Quasimolecular electronic structure of the spin-liquid candidate Ba${}_3$InIr${}_2$O${}_9$
• Quasimolecular $J_{\mathrm{tet}}$=3/2 moments in the cluster Mott insulator GaTa${}_4$Se${}_8$
• Clusterization transition between cluster Mott insulators on a breathing Kagomé lattice
• Direct evidence of intrinsic Mott state and its layer-parity oscillation in a breathing kagome crystal down to monolayer
• Quasimolecular electronic structure of the trimer iridate Ba${}_4$NbIr${}_3$O${}_{12}$
• Z${}_2$ topological orders in kagomé dipolar systems: Feedback from Rydberg quantum simulator
• Flux-induced midgap states between strain-engineered flat bands