Dynamic fingerprint of fractionalized excitations in single-crystalline Cu3Zn(OH)6FBr

AbstractBeyond the absence of long-range magnetic orders, the most prominent feature of the elusive quantum spin liquid (QSL) state is the existence of fractionalized spin excitations, i.e., spinons. When the system orders, the spin-wave excitation appears as the bound state of the spinon-antispinon pair. Although scarcely reported, a direct comparison between similar compounds illustrates the evolution from spinon to magnon. Here, we perform the Raman scattering on single crystals of two quantum kagome antiferromagnets, of which one is the kagome QSL candidate Cu3Zn(OH)6FBr, and another is an antiferromagnetically ordered compound EuCu3(OH)6Cl3. In Cu3Zn(OH)6FBr, we identify a unique one spinon-antispinon pair component in the E2g magnetic Raman continuum, providing strong evidence for deconfined spinon excitations. In contrast, a sharp magnon peak emerges from the one-pair spinon continuum in the Eg magnetic Raman response once EuCu3(OH)6Cl3 undergoes the antiferromagnetic order transition. From the comparative Raman studies, we can regard the magnon mode as the spinon-antispinon bound state, and the spinon confinement drives the magnetic ordering.

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Dynamic fingerprint of fractionalized excitations in single-crystalline Cu3Zn(OH)6FBr

10.21203/rs.3.rs-98671/v1 ◽

2021 ◽

Author(s):

Ying Fu ◽

Miao-Ling Lin ◽

Le Wang ◽

Qiye Liu ◽

Lianglong Huang ◽

...

Keyword(s):

Magnetic Ordering ◽

Bound State ◽

Quantum Spin ◽

Antiferromagnetic Order ◽

Spin Liquid ◽

Spin Excitations ◽

Magnetic Orders ◽

Pair Component ◽

The One ◽

Quantum Spin Liquid

Abstract Beyond the absence of long-range magnetic orders, the most prominent feature of the elusive quantum spin liquid (QSL) state is the existence of fractionalized spin excitations, i.e., spinons. When the system orders, the spin-wave excitation appears as the bound state of the spinon-antispinon pair. Although scarcely reported, a direct comparison between similar compounds illustrates the evolution from spinon to magnon. Here, we perform the Raman scattering on single crystals of two quantum kagome antiferromagnets, of which one is the kagome QSL candidate Cu3Zn(OH)6FBr, and another is an antiferromagnetically ordered compound EuCu3(OH)6Cl3. In Cu3Zn(OH)6FBr, we identify a unique one spinon-antispinon pair component in the E2g magnetic Raman continuum, providing strong evidence for deconfined spinon excitations. In contrast, a sharp magnon peak emerges from the one-pair spinon continuum in the Eg magnetic Raman response once EuCu3(OH)6Cl3 undergoes the antiferromagnetic order transition. From the comparative Raman studies, we can regard the magnon mode as the spinon-antispinon bound state, and the spinon confinement drives the magnetic ordering.

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Spin Excitations of a Proximate Kitaev Quantum Spin Liquid Realized in Cu2IrO3

Physical Review X ◽

10.1103/physrevx.9.031047 ◽

2019 ◽

Vol 9 (3) ◽

Cited By ~ 5

Author(s):

Sean K. Takahashi ◽

Jiaming Wang ◽

Alexandre Arsenault ◽

Takashi Imai ◽

Mykola Abramchuk ◽

...

Keyword(s):

Quantum Spin ◽

Spin Liquid ◽

Spin Excitations ◽

Quantum Spin Liquid

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Quantum Spin Liquid Emerging from Antiferromagnetic Order by Introducing Disorder

Physical Review Letters ◽

10.1103/physrevlett.115.077001 ◽

2015 ◽

Vol 115 (7) ◽

Cited By ~ 36

Author(s):

T. Furukawa ◽

K. Miyagawa ◽

T. Itou ◽

M. Ito ◽

H. Taniguchi ◽

...

Keyword(s):

Quantum Spin ◽

Antiferromagnetic Order ◽

Spin Liquid ◽

Quantum Spin Liquid

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Strong quantum fluctuations in a quantum spin liquid candidate with a Co-based triangular lattice

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1906483116 ◽

2019 ◽

Vol 116 (29) ◽

pp. 14505-14510 ◽

Cited By ~ 10

Author(s):

Ruidan Zhong ◽

Shu Guo ◽

Guangyong Xu ◽

Zhijun Xu ◽

Robert J. Cava

Keyword(s):

Triangular Lattice ◽

Magnetic Ordering ◽

Quantum Fluctuations ◽

Quantum Spin ◽

Low Energy ◽

Spin Liquid ◽

Effective Spin ◽

Experimental Realization ◽

Quantum Spin Liquid ◽

Applied Fields

Currently under active study in condensed matter physics, both theoretically and experimentally, are quantum spin liquid (QSL) states, in which no long-range magnetic ordering appears at low temperatures due to strong quantum fluctuations of the magnetic moments. The existing QSL candidates all have their intrinsic disadvantages, however, and solid evidence for quantum fluctuations is scarce. Here, we report a previously unreported compound, Na2BaCo(PO4)2, a geometrically frustrated system with effective spin-1/2 local moments for Co2+ ions on an isotropic 2-dimensional (2D) triangular lattice. Magnetic susceptibility and neutron scattering experiments show no magnetic ordering down to 0.05 K. Thermodynamic measurements show that there is a tremendous amount of magnetic entropy present below 1 K in 0-applied magnetic field. The presence of localized low-energy spin fluctuations is revealed by inelastic neutron measurements. At low applied fields, these spin excitations are confined to low energy and contribute to the anomalously large specific heat. In larger applied fields, the system reverts to normal behavior as evident by both neutron and thermodynamic results. Our experimental characterization thus reveals that this material is an excellent candidate for the experimental realization of a QSL state.

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Quantum spin liquid and cluster Mott insulator phases in the Mo3O8 magnets

npj Quantum Materials ◽

10.1038/s41535-021-00316-7 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

S. A. Nikolaev ◽

I. V. Solovyev ◽

S. V. Streltsov

Keyword(s):

Charge Order ◽

Quantum Spin ◽

Antiferromagnetic Order ◽

Spin Liquid ◽

Coulomb Interactions ◽

Kagome Lattice ◽

Kagomé Lattice ◽

Quantum Cluster ◽

Quantum Spin Liquid ◽

Microscopic Origin

AbstractWe unveil the microscopic origin of largely debated magnetism in the Mo3O8 quantum systems. Upon considering an extended Hubbard model at 1/6 filling on the anisotropic kagomé lattice formed by the Mo atoms, we argue that its ground state is determined by the competition between kinetic energy and intersite Coulomb interactions, which is controlled by the trimerisation of the kagomé lattice into the Mo3O13 clusters, and the sign of hopping parameters, specifying the electron localisation at such clusters. Based on first-principles calculations, we show that the strong interaction limit reveals a plaquette charge order with unpaired spins at the resonating hexagons that can be realised in LiZn2Mo3O8, and whose origin is solely related to the opposite signs of intracluster and intercluster hoppings, in contrast to all previous scenarios. On the other hand, both Li2InMo3O8 and Li2ScMo3O8 are demonstrated to fall into the weak interaction limit where the electrons are well localised at the Mo3O13 clusters. While the former is found to exhibit long-range antiferromagnetic order, the latter is more likely to reveal short-range order with quantum spin liquid-like excitations. Our results not only reproduce most of the experimentally observed features of the Mo3O8 systems, but will also help to describe various properties in other quantum cluster magnets.

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Proximate ferromagnetic state in the Kitaev model material α-RuCl3

Nature Communications ◽

10.1038/s41467-021-24722-4 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

H. Suzuki ◽

H. Liu ◽

J. Bertinshaw ◽

K. Ueda ◽

H. Kim ◽

...

Keyword(s):

Ferromagnetic State ◽

Model Material ◽

Quantum Spin ◽

Antiferromagnetic Order ◽

Spin Liquid ◽

Theoretical Understanding ◽

Local Maxima ◽

Scattering Study ◽

Kitaev Model ◽

Quantum Spin Liquid

Abstractα-RuCl3 is a major candidate for the realization of the Kitaev quantum spin liquid, but its zigzag antiferromagnetic order at low temperatures indicates deviations from the Kitaev model. We have quantified the spin Hamiltonian of α-RuCl3 by a resonant inelastic x-ray scattering study at the Ru L3 absorption edge. In the paramagnetic state, the quasi-elastic intensity of magnetic excitations has a broad maximum around the zone center without any local maxima at the zigzag magnetic Bragg wavevectors. This finding implies that the zigzag order is fragile and readily destabilized by competing ferromagnetic correlations. The classical ground state of the experimentally determined Hamiltonian is actually ferromagnetic. The zigzag state is stabilized by quantum fluctuations, leaving ferromagnetism – along with the Kitaev spin liquid – as energetically proximate metastable states. The three closely competing states and their collective excitations hold the key to the theoretical understanding of the unusual properties of α-RuCl3 in magnetic fields.

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Gapless Spin Excitations in the Field-Induced Quantum Spin Liquid Phase of α−RuCl3

Physical Review Letters ◽

10.1103/physrevlett.119.227208 ◽

2017 ◽

Vol 119 (22) ◽

Cited By ~ 101

Author(s):

Jiacheng Zheng ◽

Kejing Ran ◽

Tianrun Li ◽

Jinghui Wang ◽

Pengshuai Wang ◽

...

Keyword(s):

Liquid Phase ◽

Quantum Spin ◽

Spin Liquid ◽

Spin Excitations ◽

Quantum Spin Liquid

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S = ½ Heterospin Frustration in a Metal‒Fullerene-Bonded Semiconductive Antiferromagnet

10.21203/rs.3.rs-701194/v1 ◽

2021 ◽

Author(s):

Yongbing Shen ◽

Mengxing Cui ◽

Shinya Takaishi ◽

Takao Tsumuraya ◽

Akihiro Otsuka ◽

...

Keyword(s):

Lithium Ion ◽

Magnetic Ordering ◽

Quantum Spin ◽

Spin Liquid ◽

Potential Candidate ◽

Paramagnetic Resonance ◽

Triplet Ground State ◽

Redox Active ◽

Quantum Spin Liquid ◽

Electron Paramagnetic

Abstract Lithium-ion-encapsulated fullerenes (Li+@C60) are 3D superatoms with rich oxidative states. However, no current studies have reported Li+@C60 as ligands. Here, we report a conductive and magnetically frustrated metal–fullerene-bonded framework {[Cu4(Li+@C60)(L)(py)4](NTf2)(hexane)n (1) prepared from redox-active dinuclear metal complex Cu2(L)(py)4 and lithium-ion-encapsulated fullerene salt (Li+@C60)(NTf2−), where ligand L denotes 1,2,4,5-tetrakis(methanesulfonamido)benzene, py pyridine, and NTf2− the bis(trifluoromethane)sulfonamide anion. Electron donor Cu2(L)(py)2 bonds to acceptor Li+@C60 via eight Cu‒C bonds. Cu–C bond formation stems from spontaneous charge transfer (CT) between Cu2(L)(py)4 and (Li+@C60)(NTf2−) by removing the two-terminal py molecules, yielding triplet ground state [Cu2(L)(py)2]+(Li+@C•‒ 60), evidenced by absorption and electron paramagnetic resonance (EPR) spectra, magnetic properties, and quantum chemical calculations. Moreover, Li+@C•‒ 60 radicals (S = ½) and Cu2+ ions (S = ½) interact antiferromagnetically in triangular spin lattices in the absence of long-range magnetic ordering up to 1.8 K; thus, compound 1 is a potential candidate for an S = ½ quantum spin liquid.

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