Quantum liquid from strange frustration in the trimer magnet Ba4Ir3O10

Abstract

Quantum spin systems such as magnetic insulators usually show classical magnetic order, but such classical states can give way to quantum liquids with exotic entanglement through two known mechanisms of frustration: geometric frustration in lattices with triangle motifs, and spin-orbit-coupling frustration in the exactly solvable quantum liquid of Kitaev's honeycomb lattice. Here we present the experimental observation of a new kind of frustrated quantum liquid arising in an unlikely place: the magnetic insulator Ba4Ir3O10 where Ir3O12 trimers form an unfrustrated square lattice. Experimentally we find a quantum liquid state persisting down to 0.2 K that is stabilized by strong antiferromagnetic interaction with Curie-Weiss temperature - 766 K. The astonishing frustration parameter of 3800 is beyond any known iridate thus far. Heat capacity and thermal conductivity are both linear at low temperatures, a familiar feature in metals but here in an insulator pointing to an exotic quantum liquid state. A mere 2% Sr substitution for Ba produces long-range order at 130 K and destroys the linear-T features. Although the Ir4+(5d5) ions in Ba4Ir3O10 appear to form Ir3O12 trimers of face-sharing IrO6 octahedra, we propose that intra-trimer exchange is reduced and the lattice recombines into an array of coupled 1D chains with additional spins. An extreme limit of decoupled 1D chains can explain most but not all of the striking experimental observations, indicating that the inter-chain coupling plays an important role in the novel frustration mechanism leading to this quantum liquid.

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• Emergence of spinons in layered trimer iridate Ba4Ir3O10
• Quest for New Quantum States via Field-Editing Technology
• Quantum phase transitions and composite excitations of antiferromagnetic spin trimer chains in a magnetic field
• Structural and Magnetic Transitions in the Planar Antiferromagnet Ba${}_4$Ir${}_3$O${}_{10}$
• Dimerization and spin-decoupling in two-leg Heisenberg ladder with frustrated trimer rungs
• Spin Frustration and a `Half Fire, Half Ice' Critical Point from Nonuniform $g$-Factors
• Spinons and damped phonons in spin-1/2 quantum-liquid Ba${}_4$Ir${}_3$O${}_{10}$ observed by Raman scattering
• Magnon, doublon and quarton excitations in 2D S=1/2 trimerized Heisenberg models
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• Resonant inelastic x-ray scattering spectra of spinon, doublon, and quarton excitations of a spin-$\frac{1}{2}$ antiferromagnetic Heisenberg trimer chain
• Quasimolecular electronic structure of the trimer iridate Ba${}_4$NbIr${}_3$O${}_{12}$
• Magnetic Ground State and Spin Excitations in the 2D Trimerized Collinear-II Lattice Antiferromagnet Li2Ni3P4O14
• Structural origin of the Jeff=1/2 antiferromagnetic phase in Ga-doped Sr2IrO4
• SrCu(OH)${}_3$Cl, an ideal isolated equilateral triangle spin $S$ = 1/2 model system