Abstract
Quantum spin systems such as magnetic insulators usually show 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. The crystal structure shows no apparent spin chains. Experimentally we find a quantum liquid state persisting down to 0.2 K that is stabilized by strong antiferromagnetic interaction with Curie–Weiss temperature ranging from −766 to −169 K due to magnetic anisotropy. The anisotropy-averaged frustration parameter is 2000, seldom seen in iridates. 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 frustration mechanism leading to this quantum liquid.
Highlights
Quantum spin systems can enter unusual quantum phases of matter known as quantum liquids. The first such quantum liquids were discovered in one-dimensional systems that are known as Tomonaga–Luttinger liquids; a second class of quantum liquids can occur in two or higher dimensions and goes by the name quantum spin liquids[1]
We propose a theoretical scenario of a quantum liquid state that emerges from a recombination of the Ir3O12 trimers and
The face-sharing geometry for IrO6 octahedra is believed to produce stronger magnetic exchange, e.g. due to the shorter Ir-Ir distance (2.576 Å)[26]. Under this assumption the Ir3O12 trimers in Ba4Ir3O10 would form the basic magnetic unit, with an effective spin-1/2 Kramer’s doublet on each trimer, and the lattice of trimers would determine all low-energy properties. From this point of view, the magnetic phenomenology in Ba4Ir3O10 is puzzling: its observed frustration is inconsistent with the trimer picture
Summary
Quantum spin systems can enter unusual quantum phases of matter known as quantum liquids The first such quantum liquids were discovered in one-dimensional systems that are known as Tomonaga–Luttinger liquids; a second class of quantum liquids can occur in two or higher dimensions and goes by the name quantum spin liquids[1]. These are quantum phases with fractionalized excitations that cannot be adiabatically connected to a stack of 1D systems. A more recent development was the theoretical discovery by Kitaev[4] of a second kind of frustration mechanism, manifested in an exactly solvable spin-liquid model on the honeycomb lattice with strong spin-orbit interactions (SOI).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
