Gapless spin liquid in a square-kagome lattice antiferromagnet

Abstract

Observation of a quantum spin liquid (QSL) state is one of the most important goals in condensed-matter physics, as well as the development of new spintronic devices that support next-generation industries. The QSL in two dimensional quantum spin systems is expected to be due to geometrical magnetic frustration, and thus a kagome-based lattice is the most probable playground for QSL. Here, we report the first experimental results of the QSL state on a square-kagome quantum antiferromagnet, KCu 6 AlBiO 4 (SO 4) 5 Cl. Comprehensive experimental studies via magnetic susceptibility, magnetisation, heat capacity, muon spin relaxation (μSR), and inelastic neutron scattering (INS) measurements reveal the formation of a gapless QSL at very low temperatures close to the ground state. The QSL behavior cannot be explained fully by a frustrated Heisenberg model with nearest-neighbor exchange interactions, providing a theoretical challenge to unveil the nature of the QSL state.

Pinwheel valence bond crystal ground state of the spin- 12 Heisenberg antiferromagnet on the shuriken lattice

“…This finding is at variance with that obtained within an extended (beyond nearest-neighbor valence bond basis) quantum dimer model framework which argued for a loop-6 VBC [13]. Given that KCu 6 AlBiO 4 (SO 4 ) 5 Cl [3] realizes a gapless spin liquid, and consideration of a generalized model with J = J and further neighbor couplings fails to reproduce the neutron scattering profile as shown in Ref. [3], possibly hints at the role of non-negligible Dzyaloshinskii-Moriya interactions at play, and the investigation of these interactions would constitute an important future direction of research.…”

“…Given that KCu 6 AlBiO 4 (SO 4 ) 5 Cl [3] realizes a gapless spin liquid, and consideration of a generalized model with J = J and further neighbor couplings fails to reproduce the neutron scattering profile as shown in Ref. [3], possibly hints at the role of non-negligible Dzyaloshinskii-Moriya interactions at play, and the investigation of these interactions would constitute an important future direction of research. Finally, given that (lattice) nematic topological quantum spin liquids have been proposed as competitive [11], a projective symmetry group classification [18] of fermionic mean-field Ansätze of symmetric and nematic Z 2 spin liquids, and a subsequent analysis of the energies and correlation functions of the corresponding Gutzwiller-projected spin states would constitute an important direction for future investigations.…”

“…1). Following the recent experimental reporting of a gapless spin liquid in a first material realization of the shuriken geometry by spin S = 1/2C u 2+ magnetic ions in KCu 6 AlBiO 4 (SO 4 ) 5 Cl [3], there is renewed interest in exploring the nature of frustration-induced phases in the quantum Heisenberg antiferromagnet.…”

Probing resonating valence bond states in artificial quantum magnets

“…The precisely engineered finite-size quantum many-body systems demonstrated here may serve as versatile analog quantum simulators 31 , 34 , 38 , 39 because they can be assembled, modified, and probed in situ with single-spin selectivity. The spin plaquette constructed here is the fundamental building block of the square lattice spin liquids 40 . A unique opportunity provided by the STM is to explore the real-space response of the spin liquid to point defects such as individual pinned magnetic moments, which can better reveal the character of the quantum spin liquids 41 , 42 .…”

Magnetic Field Induced Quantum Spin Liquid in the Two Coupled Trillium Lattices of K2Ni2(SOŽivković1, Favre2, Mejía3 et al. 2021Phys. Rev. Lett.23040View full textAdd to dashboardCite

“…( 1) (blue symbols). Below T ∼ 1 K, the extracted parameters attain a constant value, a feature often associated with a highly dynamic nature of QSLs [31][32][33]. We point out that the value of the exponent β ≃ 2 is indicative of a specific type of a correlated spin system based on spin singlets [34].…”