Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2504.06491

Identifying Universal Spin Excitations in Spin-1/2 Kagome Quantum Spin Liquid Materials

Aaron Breidenbach, Arthur C. Campello, Jiajia Wen, Hong‐Chen Jiang, Daniel M. Pajerowski, Rebecca W. Smaha, Y. S. Lee

Published Apr 8, 2025• 0 citations
arXivHTMLPDF

Abstract

A quantum spin liquid (QSL) is an exotic quantum state of matter characterized by fluctuating spins which may exhibit long-range entanglement. Among the possible host candidates for a QSL ground state, the $S$=1/2 kagome lattice antiferromagnet is particularly promising. Using high resolution inelastic neutron scattering measurements on Zn-barlowite (Zn$_\mathrm{x}$Cu$_\mathrm{4-x}$(OD)$_\mathrm{6}$FBr, $x\simeq 0.80$), we measure a spin excitation spectrum consistent with a QSL ground state. Continuum scattering above $\sim$1 meV matches that of herbertsmithite (Zn$_\mathrm{x}$Cu$_\mathrm{4-x}$(OD)$_6$Cl$_2$, $x\simeq 0.85$), another prominent kagome QSL material, indicating universal spinon excitations. A detailed analysis of the spin-spin correlations, compared with density matrix renormalization group calculations, further indicate a QSL ground state for the physically relevant Hamiltonian parameters. The measured spectra in Zn-barlowite are consistent with gapped behavior with a gap size $Δ= 1.1(2)$ meV. Comparison with a simple pair correlation model allows us to clearly distinguish intrinsic kagome correlations from impurity-induced correlations. Our results clarify the behavior that is universal within this important family of QSL candidate materials.

DOI
10.48550/arxiv.2504.06491

Related papers

Quantifying the phase diagram and Hamiltonian of S = 1/2 kagome antiferromagnets: bridging theory and experiment

Shengtao Jiang, Arthur C. Campello, Wei He +4 more

Abstract Spin-1/2 kagome antiferromagnets are leading candidates for realizing quantum spin liquid (QSL) ground states. While QSL ground states are predicted for the pure Heisenberg model, understanding the robustness of the QSL to additional interactions that may be present in real materials is a forefront question in the field. Here we employ large-scale density-matrix renormalization group simulations to investigate the effects of next-nearest neighbor exchange couplings J 2 and Dzyaloshinskii-Moriya interactions D , which are relevant to understanding the prototypical kagome materials herbertsmithite and Zn-barlowite. By utilizing clusters as large as XC12 and extrapolating the results to the thermodynamic limit, we precisely delineate the scope of the QSL phase, which remains robust across an expanded parameter range of J 2 and D . Direct comparison of the simulated static and dynamic spin structure factors with inelastic neutron scattering reveals the parameter space of the Hamiltonians for herbertsmithite and Zn-barlowite, and, importantly, provides compelling evidence that both materials exist within the QSL phase. These results establish a powerful convergence of theory and experiment in this most elusive state of matter.

arXiv:2504.07387•npj Computational Materials•Jan 15, 2026•1 citation

Evidence for a Z$_2$ topological ordered quantum spin liquid in a kagome-lattice antiferromagnet

Wei Yuan, Zili Feng, Wiebke Lohstroh +12 more

A quantum spin liquid with a $Z_2$ topological order has long been thought to be important for the application of quantum computing and may be related to high-temperature superconductivity. While a two-dimensional kagome antiferromagnet may host such a state, strong experimental evidences are still lacking. Here we show that the spin excitations from the kagome planes in magnetically ordered Cu$_4$(OD)$_6$FBr and non-magnetically ordered Cu$_3$Zn(OD)$_6$FBr are similarly gapped although the content of inter-kagome-layer Cu$^{2+}$ ions changes dramatically. This suggests that the spin triplet gap and continuum of the intrinsic kagome antiferromagnet are robust against the interlayer magnetic impurities. Our results show that the ground state of Cu$_3$Zn(OD)$_6$FBr is a gapped quantum spin liquid with Z$_2$ topological order.

arXiv:1710.02991•Bulletin of the American Physical Society•Oct 9, 2017•11 citations

Dynamical Spectral Function of the Kagome Quantum Spin Liquid

Jiahang Hu, Runze Chi, Yibin Guo +3 more

Quantum spin liquids (QSLs) host exotic fractionalized magnetic and gauge-field excitations whose microscopic origins and experimental verification remain frustratingly elusive. In the absence of static magnetic order, the spin excitation spectrum constitutes the crucial probe of QSL behavior, but its theoretical computation is a serious challenge. Here we employ state-of-the-art tensor-network methods to obtain the full dynamical spectral function of the $J_1$-$J_2$ kagome Heisenberg model and benchmark our results by tracking their evolution across the magnetically ordered and QSL phases. Reducing $|J_2|/J_1$ causes increasingly strong spin-wave renormalization, flattening these modes then merging them into a continuum characteristic of deconfined spinons at all finite energies in the QSL. The low-energy continuum and the occurrence of gap closure at multiple high-symmetry points identify this gapless QSL as the U(1) Dirac spin liquid. These results establish a unified understanding of spin excitations in highly frustrated quantum magnets and provide clear spectral fingerprints for experimental detection in candidate kagome QSL materials.

cond-mat.str-elCross-listedarXiv:2512.18831•Physical Review Letters•Dec 23, 2025•0 citations

Two quantum spin liquid states coexisting in the kagome antiferromagnet herbertsmithite

Arthur C. Campello, Shengtao Jiang, Wei He +5 more

Herbertsmithite (ZnCu$_3$(OH)$_6$Cl$_2$) is one of the most extensively studied quantum spin liquid (QSL) candidates, yet the precise nature of its ground state remains unresolved. Here, we compare the results of high-resolution inelastic neutron scattering on single crystals of herbertsmithite (Zn$_\mathrm{x}$Cu$_\mathrm{4-x}$(OD)$_6$Cl$_2$, $x\simeq 0.85$) with large-scale density-matrix renormalization group (DMRG) and dynamical DMRG simulations to benchmark the spin Hamiltonian and uncover fundamental properties of the ground state. The measured spin correlations determine an energy density for the Heisenberg model that closely matches simulations, an essential verification of the Hamiltonian. In parallel, DMRG simulations reveal two nearly degenerate QSL states. Both preserve translational symmetry, but one retains the lattice point-group symmetries whereas the other develops anisotropic spin correlations that break point-group symmetry. These two QSLs have distinct spin structure factors, and, remarkably, close agreement with the neutron spectra is achieved with an admixture of the two states. Our results establish a quantitative correspondence between neutron scattering and simulations, and suggest that herbertsmithite realizes a regime in which two proximate gapped QSL states coexist.

arXiv:2610.24065•Oct 16, 2026•0 citations

Entanglement signatures of emergent Dirac fermions: Kagome spin liquid and quantum criticality

Wei Zhu, Xiao Chen, Yin-Chen He +1 more

Quantum spin liquids (QSLs) are exotic phases of matter that host fractionalized excitations. It is difficult for local probes to characterize QSL, whereas quantum entanglement can serve as a powerful diagnostic tool due to its nonlocality. The kagome antiferromagnetic Heisenberg model is one of the most studied and experimentally relevant models for QSL, but its solution remains under debate. Here, we perform a numerical Aharonov-Bohm experiment on this model and uncover universal features of the entanglement entropy. By means of the density matrix renormalization group, we reveal the entanglement signatures of emergent Dirac spinons, which are the fractionalized excitations of the QSL. This scheme provides qualitative insights into the nature of kagome QSL and can be used to study other quantum states of matter. As a concrete example, we also benchmark our methods on an interacting quantum critical point between a Dirac semimetal and a charge-ordered phase.

arXiv:1801.06177•Science Advances•Nov 2, 2018•57 citations

Strong relevance of zinc impurities in spin- 12 kagome quantum antiferromagnets: A variational study

Jianhua Yang, Tao Li

Copper hydroxyhalide materials herbertsmithite ${\mathrm{ZnCu}}_{3}{(\mathrm{OH})}_{6}{\mathrm{Cl}}_{2}$ and Zn-barlowite ${\mathrm{ZnCu}}_{3}{(\mathrm{OH})}_{6}\mathrm{FrBr}$ are thought to be the best realizations of the spin-1/2 kagome quantum antiferromagnetic Heisenberg model and are widely believed to host a spin liquid ground state. However, the exact nature of such a novel state of matter is still under strong debate, partly due to the complication related to the occupation disorder between the zinc and the copper ions in these systems. More specifically, some nonmagnetic ${\mathrm{Zn}}^{2+}$ ions in the system may occupy the ${\mathrm{Cu}}^{2+}$ site within the kagome plane and some spin-$1/2\phantom{\rule{4pt}{0ex}}{\mathrm{Cu}}^{2+}$ ions may occupy the ${\mathrm{Zn}}^{2+}$ site between the kagome planes. Both types of impurity can have a nontrivial effect on the dynamical behavior of the antiferromagnetically coupled ${\mathrm{Cu}}^{2+}$ spins on the kagome planes. Recent nuclear magnetic resonance measurements indicate that the magnetic response of the kagome plane is significantly spatial inhomogeneous, even though the content of the misplaced zinc or copper ions is very small. Here we use extensive variational optimization to show that the well-known U(1) Dirac spin liquid state is extremely sensitive to the introduction of the nonmagnetic ${\mathrm{Zn}}^{2+}$ impurity in the kagome plane. More specifically, we find that the zinc impurities can significantly reorganize the local spin correlation pattern around them and induce strong spatial oscillation in the magnetic response of the system. We argue that this is a general trend in highly frustrated quantum magnet systems, in which the nonmagnetic impurity may act as a strongly relevant perturbation on the emergent resonating valence bond structure in their spin liquid ground state. We also argue that the strong spatial oscillation in the magnetic response should be attributed to the free moment released by the doped ${\mathrm{Zn}}^{2+}$ ions and may serve as the smoking-gun evidence for the Dirac node in the U(1) Dirac spin liquid state on the kagome lattice.

arXiv:2309.04363•Physical review. B./Physical review. B•Mar 1, 2024•2 citations
A quantum spin liquid (QSL) is an exotic quantum state of matter characterized by fluctuating spins which may exhibit long-range entanglement. Among the possible host candidates for a QSL ground state, the SSS=1/2 kagome lattice antiferromagnet is particularly promising. Using high resolution inelastic neutron scattering measurements on Zn-barlowite (Znx_\mathrm{x}x​Cu4−x_\mathrm{4-x}4−x​(OD)6_\mathrm{6}6​FBr, x≃0.80x\simeq 0.80x≃0.80), we measure a spin excitation spectrum consistent with a QSL ground state. Continuum scattering above ∼\sim∼1 meV matches that of herbertsmithite (Znx_\mathrm{x}x​Cu4−x_\mathrm{4-x}4−x​(OD)6_66​Cl2_22​, x≃0.85x\simeq 0.85x≃0.85), another prominent kagome QSL material, indicating universal spinon excitations. A detailed analysis of the spin-spin correlations, compared with density matrix renormalization group calculations, further indicate a QSL ground state for the physically relevant Hamiltonian parameters. The measured spectra in Zn-barlowite are consistent with gapped behavior with a gap size Δ=1.1(2)Δ= 1.1(2)Δ=1.1(2) meV. Comparison with a simple pair correlation model allows us to clearly distinguish intrinsic kagome correlations from impurity-induced correlations. Our results clarify the behavior that is universal within this important family of QSL candidate materials.
Abstract Spin-1/2 kagome antiferromagnets are leading candidates for realizing quantum spin liquid (QSL) ground states. While QSL ground states are predicted for the pure Heisenberg model, understanding the robustness of the QSL to additional interactions that may be present in real materials is a forefront question in the field. Here we employ large-scale density-matrix renormalization group simulations to investigate the effects of next-nearest neighbor exchange couplings J 2 and Dzyaloshinskii-Moriya interactions D , which are relevant to understanding the prototypical kagome materials herbertsmithite and Zn-barlowite. By utilizing clusters as large as XC12 and extrapolating the results to the thermodynamic limit, we precisely delineate the scope of the QSL phase, which remains robust across an expanded parameter range of J 2 and D . Direct comparison of the simulated static and dynamic spin structure factors with inelastic neutron scattering reveals the parameter space of the Hamiltonians for herbertsmithite and Zn-barlowite, and, importantly, provides compelling evidence that both materials exist within the QSL phase. These results establish a powerful convergence of theory and experiment in this most elusive state of matter.
Evidence for a Z2_22​ topological ordered quantum spin liquid in a kagome-lattice antiferromagnet
A quantum spin liquid with a Z2Z_2Z2​ topological order has long been thought to be important for the application of quantum computing and may be related to high-temperature superconductivity. While a two-dimensional kagome antiferromagnet may host such a state, strong experimental evidences are still lacking. Here we show that the spin excitations from the kagome planes in magnetically ordered Cu4_44​(OD)6_66​FBr and non-magnetically ordered Cu3_33​Zn(OD)6_66​FBr are similarly gapped although the content of inter-kagome-layer Cu2+^{2+}2+ ions changes dramatically. This suggests that the spin triplet gap and continuum of the intrinsic kagome antiferromagnet are robust against the interlayer magnetic impurities. Our results show that the ground state of Cu3_33​Zn(OD)6_66​FBr is a gapped quantum spin liquid with Z2_22​ topological order.
Quantum spin liquids (QSLs) host exotic fractionalized magnetic and gauge-field excitations whose microscopic origins and experimental verification remain frustratingly elusive. In the absence of static magnetic order, the spin excitation spectrum constitutes the crucial probe of QSL behavior, but its theoretical computation is a serious challenge. Here we employ state-of-the-art tensor-network methods to obtain the full dynamical spectral function of the J1J_1J1​-J2J_2J2​ kagome Heisenberg model and benchmark our results by tracking their evolution across the magnetically ordered and QSL phases. Reducing ∣J2∣/J1|J_2|/J_1∣J2​∣/J1​ causes increasingly strong spin-wave renormalization, flattening these modes then merging them into a continuum characteristic of deconfined spinons at all finite energies in the QSL. The low-energy continuum and the occurrence of gap closure at multiple high-symmetry points identify this gapless QSL as the U(1) Dirac spin liquid. These results establish a unified understanding of spin excitations in highly frustrated quantum magnets and provide clear spectral fingerprints for experimental detection in candidate kagome QSL materials.
Herbertsmithite (ZnCu3_33​(OH)6_66​Cl2_22​) is one of the most extensively studied quantum spin liquid (QSL) candidates, yet the precise nature of its ground state remains unresolved. Here, we compare the results of high-resolution inelastic neutron scattering on single crystals of herbertsmithite (Znx_\mathrm{x}x​Cu4−x_\mathrm{4-x}4−x​(OD)6_66​Cl2_22​, x≃0.85x\simeq 0.85x≃0.85) with large-scale density-matrix renormalization group (DMRG) and dynamical DMRG simulations to benchmark the spin Hamiltonian and uncover fundamental properties of the ground state. The measured spin correlations determine an energy density for the Heisenberg model that closely matches simulations, an essential verification of the Hamiltonian. In parallel, DMRG simulations reveal two nearly degenerate QSL states. Both preserve translational symmetry, but one retains the lattice point-group symmetries whereas the other develops anisotropic spin correlations that break point-group symmetry. These two QSLs have distinct spin structure factors, and, remarkably, close agreement with the neutron spectra is achieved with an admixture of the two states. Our results establish a quantitative correspondence between neutron scattering and simulations, and suggest that herbertsmithite realizes a regime in which two proximate gapped QSL states coexist.
Quantum spin liquids (QSLs) are exotic phases of matter that host fractionalized excitations. It is difficult for local probes to characterize QSL, whereas quantum entanglement can serve as a powerful diagnostic tool due to its nonlocality. The kagome antiferromagnetic Heisenberg model is one of the most studied and experimentally relevant models for QSL, but its solution remains under debate. Here, we perform a numerical Aharonov-Bohm experiment on this model and uncover universal features of the entanglement entropy. By means of the density matrix renormalization group, we reveal the entanglement signatures of emergent Dirac spinons, which are the fractionalized excitations of the QSL. This scheme provides qualitative insights into the nature of kagome QSL and can be used to study other quantum states of matter. As a concrete example, we also benchmark our methods on an interacting quantum critical point between a Dirac semimetal and a charge-ordered phase.
Copper hydroxyhalide materials herbertsmithite ZnCu3(OH)6Cl2{\mathrm{ZnCu}}_{3}{(\mathrm{OH})}_{6}{\mathrm{Cl}}_{2}ZnCu3​(OH)6​Cl2​ and Zn-barlowite ZnCu3(OH)6FrBr{\mathrm{ZnCu}}_{3}{(\mathrm{OH})}_{6}\mathrm{FrBr}ZnCu3​(OH)6​FrBr are thought to be the best realizations of the spin-1/2 kagome quantum antiferromagnetic Heisenberg model and are widely believed to host a spin liquid ground state. However, the exact nature of such a novel state of matter is still under strong debate, partly due to the complication related to the occupation disorder between the zinc and the copper ions in these systems. More specifically, some nonmagnetic Zn2+{\mathrm{Zn}}^{2+}Zn2+ ions in the system may occupy the Cu2+{\mathrm{Cu}}^{2+}Cu2+ site within the kagome plane and some spin-1/2Cu2+1/2\phantom{\rule{4pt}{0ex}}{\mathrm{Cu}}^{2+}1/2Cu2+ ions may occupy the Zn2+{\mathrm{Zn}}^{2+}Zn2+ site between the kagome planes. Both types of impurity can have a nontrivial effect on the dynamical behavior of the antiferromagnetically coupled Cu2+{\mathrm{Cu}}^{2+}Cu2+ spins on the kagome planes. Recent nuclear magnetic resonance measurements indicate that the magnetic response of the kagome plane is significantly spatial inhomogeneous, even though the content of the misplaced zinc or copper ions is very small. Here we use extensive variational optimization to show that the well-known U(1) Dirac spin liquid state is extremely sensitive to the introduction of the nonmagnetic Zn2+{\mathrm{Zn}}^{2+}Zn2+ impurity in the kagome plane. More specifically, we find that the zinc impurities can significantly reorganize the local spin correlation pattern around them and induce strong spatial oscillation in the magnetic response of the system. We argue that this is a general trend in highly frustrated quantum magnet systems, in which the nonmagnetic impurity may act as a strongly relevant perturbation on the emergent resonating valence bond structure in their spin liquid ground state. We also argue that the strong spatial oscillation in the magnetic response should be attributed to the free moment released by the doped Zn2+{\mathrm{Zn}}^{2+}Zn2+ ions and may serve as the smoking-gun evidence for the Dirac node in the U(1) Dirac spin liquid state on the kagome lattice.