Anomalous enhancement of Wilson ratio in a quantum spin liquid with strong spin-orbital entanglement: the case of Na4Ir3O8

Abstract

We present a theory for the metal-insulator transition (MIT) in the quantum-spin-liquid candidate material Na4Ir3O8. We consider an extended Hubbard model on the hyperkagome lattice, which incorporates atomic spin-orbit coupling (SOC) and multi-orbital interactions of iridium 5d electrons. This model is analyzed using the slave-rotor mean-field theory and thermodynamic properties across the MIT are studied. The ground state in the insulating side is a U(1) quantum spin liquid with spinon Fermi surfaces that consist of multiple particle-like and hole-like pockets. It is shown that the Wilson ratio in the quantum spin liquid phase is highly enhanced compared to the metallic state. This originates from the fact that the magnetic susceptibility in the quantum spin liquid phase acquires multiple enhancements due to the strong SOC, reduced band-width and on-site spin-orbital exchange, while the heat capacity does not change much across MIT. This explains the large Wilson ratio of the insulating phase observed in the previous experiment on Na4Ir3O8. Possible connections to other existing and future experiments, in particular on the metallic phase, are discussed.

6 pages, 4 figures

References in corpus (8)

• Spin-Liquid State in the S = 1/2 Hyperkagome Antiferromagnet Na4Ir3O8
• Mott Transition from a Spin Liquid to a Fermi Liquid in the Spin-Frustrated Organic Conductor kappa-(ET)2Cu2(CN)3
• Theory of a continuous Mott transition in two dimensions
• Spin-orbit effects in Na${}_4$Ir${}_3$O${}_8$, a hyper-kagomé lattice antiferromagnet
• Gapless spin liquids on the three dimensional hyper-kagome lattice of Na${}_4$Ir${}_3$O${}_8$
• Topological spin liquid on the hyper-kagome lattice of Na_4Ir_3O_8
• Na4Ir3O8 as a 3D spin liquid with fermionic spinons
• Symmetry Breaking on the Three-Dimensional Hyperkagome Lattice of Na_4Ir_3O_8

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• Competing magnetic orders and spin liquids in two- and three-dimensional kagome systems: A pseudo-fermion functional renormalization group perspective
• Molecular Quantum Materials: Electronic Phases and Charge Dynamics in Two-Dimensional Organic Solids
• Interplay of non-symmorphic symmetry and spin-orbit coupling in hyperkagome spin liquids: Applications to Na${}_4$Ir${}_3$O${}_8$
• Theoretical study of quantum spin liquids in $S=1/2$ hyper-hyperkagome magnets: classification, heat capacity, and dynamical spin structure factor
• Thermal conductivity across the metal-insulator transition in single crystalline hyperkagome Na${}_{3+x}$Ir${}_3$O${}_8$
• Phenomenological approach to hyperkagome spin liquid: gauge fields and spinons without slave particles
• Spin disorder in an Ising honeycomb chain cobaltate