Theory of the field-revealed Kitaev spin liquid

Gordon, Jacob; Catuneanu, Andrei; Sørensen, Erik S.; Kee, Hae‐Young

doi:10.1038/s41467-019-10405-8

Cited by 135 publications

(119 citation statements)

References 46 publications

(42 reference statements)

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“…The symmetry form of Eq. (14) in this case has been also established recently from numerical simulations 65 .…”

Section: Spin-orbit Torquesupporting

confidence: 60%

“…The results of Eqs. (14), (15) clearly suggest that the only torques surviving in the large energy limit are those related to non-equilibrium polarization δs + = a 0ẑ × j, which is nothing but the standard Rashba-Edelstein effect 68 . These torques have a form T n = a 0 n×(ẑ ×j) in the right-hand side of Eq.…”

Section: Spin-orbit Torquementioning

confidence: 99%

“…The coefficients a, b, and c in Eq (14). as a function of the direction of the Néel vector, nz = cos θ, for two different Fermi energies: εF = 4∆ (left panel) and εF = 16∆ (right panel).…”

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confidence: 99%

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Giant anisotropy of Gilbert damping in a Rashba honeycomb antiferromagnet

et al. 2020

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Giant Gilbert damping anisotropy is identified as a signature of strong Rashba spin-orbit coupling in a two-dimensional antiferromagnet on a honeycomb lattice. The phenomenon originates in spinorbit induced splitting of conduction electron subbands that strongly suppresses certain spin-flip processes. As a result, the spin-orbit interaction is shown to support an undamped non-equilibrium dynamical mode that corresponds to an ultrafast in-plane Néel vector precession and a constant perpendicular-to-the-plane magnetization. The phenomenon is illustrated on the basis of a two dimensional s-d like model. Spin-orbit torques and conductivity are also computed microscopically for this model. Unlike Gilbert damping these quantities are shown to reveal only a weak anisotropy that is limited to the semiconductor regime corresponding to the Fermi energy staying in a close vicinity of antiferromagnetic gap. arXiv:1911.03408v1 [cond-mat.str-el]

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“…The symmetry form of Eq. (14) in this case has been also established recently from numerical simulations 65 .…”

Section: Spin-orbit Torquesupporting

confidence: 60%

Section: Spin-orbit Torquementioning

confidence: 99%

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Giant anisotropy of Gilbert damping in a Rashba honeycomb antiferromagnet

et al. 2020

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“…Alternatively, α-RuCl 3 might be close to a quantum criti-cal point [32,33,50], which would be a very exciting scenario. Anisotropic susceptibility measurements [66] point towards significant off-diagonal Γ and Γ terms, which may also help stabilize the purported spin liquid phase at finite magnetic fields [61,67,68]. At this point it is not clear whether anisotropies between bonds or the interlayer coupling play a qualitative role, but they are also expected in a full model.…”

Section: Discussionmentioning

confidence: 99%

Dynamical and thermal magnetic properties of the Kitaev spin liquid candidate α-RuCl3

Laurell

Okamoto

2020

npj Quantum Mater.

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What is the correct low-energy spin Hamiltonian description of α-RuCl 3 ? The material is a promising Kitaev spin liquid candidate, but is also known to order magnetically, the description of which necessitates additional interaction terms. The nature of these interactions, their magnitudes and even signs, remain an open question. In this work we systematically investigate dynamical and thermodynamic magnetic properties of proposed effective Hamiltonians. We calculate zero-temperature inelastic neutron scattering (INS) intensities using exact diagonalization, and magnetic specific heat using a thermal pure quantum states method. We find that no single current model satisfactorily explains all observed phenomena of α-RuCl 3 . In particular, we find that Hamiltonians derived from first principles can capture the experimentally observed high-temperature peak in the magnetic specific heat, while overestimating the magnon energy at the zone center. In contrast, other models reproduce important features of the INS data, but do not adequately describe the magnetic specific heat. 1, 4 2 3 5 6 7 8 9 10 11 14 15 16 17 (c) Spread of proposed models FIG. 1. α-RuCl 3 . (a) The zigzag magnetic order. (b) The honeycomb lattice and its different bonds. Solid, dotted and dashed lines represent nearest, second-nearest and third-nearest neighbor bonds, respectively. (c) The variability in two nearest neighbor (NN) parameters between various proposed spin Hamiltonians for α-RuCl 3 .The Hamiltonians marked by red, bold numbers (blue, roman) are discussed in the main text (Supplemental Information). Here K 1 and J 1 are the NN Kitaev and Heisenberg couplings, respectively, and Γ is an NN symmetric off-diagonal interaction. Models with ferromagnetic (antiferromagnetic) K 1 are marked with crosses (open circles). Bond averaged values were used for anisotropic models. magnetic specific heat [25, 33, 34], NMR [30, 35], microwave absorption [36], Raman scattering [37-39], and THz spec-arXiv:1906.07579v1 [cond-mat.str-el]

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“…Remarkably, recent NMR and thermal Hall conductivity experiments on α-RuCl 3 demonstrate that one can drive the magnetically ordered phase into a QSL phase using an external mag-netic field [23,24]. To this end, various numerical tools were used to explore the possible QSL phases in the models relevant to candidate honeycomb materials with an external magnetic field [25][26][27][28][29].In this article, we theoretically address the question: What is the fate of the Kitaev QSL with increasing magnetic field (see Eq. 1), beyond the perturbative limit?…”

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confidence: 99%

Magnetic field-induced intermediate quantum spin liquid with a spinon Fermi surface

Patel

Trivedi

2019

Proc. Natl. Acad. Sci. U.S.A.

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The Kitaev model with an applied magnetic field in the H||[111] direction shows two transitions: from a non-abelian gapped quantum spin liquid (QSL) to a gapless QSL at Hc1 0.2K and a second transition at a higher field Hc2 0.35K to a gapped partially polarized phase, where K is the strength of the Kitaev exchange interaction. We identify the intermediate phase to be a gapless U(1) QSL, and determine the spin structure function S(k) and the Fermi surface S F (k) of the gapless spinons using the density matrix renormalization group (DMRG) method for large honeycomb clusters. Further calculations of static spin-spin correlations, magnetization, spin susceptibility, and finite temperature specific heat and entropy, corroborate the gapped and gapless nature of the different field-dependent phases. In the intermediate phase, the spin-spin correlations decay as a power law with distance, indicative of a gapless phase.The inspired exact solution of the Kitaev model on a twodimensional honeycomb lattice with bond dependent spin exchange interaction [1] (Eq. 1) has emerged as a paradigmatic model for quantum spin liquids (QSL). For equal bond interactions (K), the ground state of the Kitaev model is known to be a topologically non-trivial gapless QSL with fractionalized excitations. The multiple ground state degeneracy reflects the topology of the lattice manifold (2-fold degeneracy on a cylinder and 4-fold degeneracy on a torus). The promise of utilizing fractionalized excitations for applications in robust quantum computing [1][2][3][4][5] has led to considerable excitement and activity in the field from diverse directions, all the way from fundamental developments to applications. Upon breaking time-reversal symmetry (TRS), for example by applying a magnetic field, the exact solvability of the Kitaev model is lost but perturbatively it can be shown that the Kitaev gapless QSL becomes a gapped QSL phase with non-abelian anyonic excitations [1].In order to realize the exotic properties of the Kitaev model, there has been keen interest to discover Kitaev physics in materials. To this end, Mott insulators with magnetic frustration and large spin-orbit coupling have been proposed [6], leading to the discovery of α-RuCl 3 and A 2 IrO 3 (A = Na, Li). These are candidate QSL materials with the desired honeycomb geometry. Although given additional interactions beyond the Kitaev interaction in materials, there is still controversy about the regimes where Kitaev physics can be accessed [7][8][9][10][11][12]. Additionally, triangular and Kagome lattice with spin frustration has also been proposed as a candidate for a QSL [13][14][15][16][17][18][19]. In this context, organics such as κ-(BEDT-TTF) 2 Cu 2 (CN) 3 [20] and EtMe 3 Sb[Pd(dmit) 2 ] 2 [21], the transition metal dichalcogenides 1T-TaS 2 [19] and a large family of rare-earth dichalcogenides AReX 2 (A = alkali or monovalent ions, Re = rare earth, X = O, S, Se) [22] have been explored. Remarkably, recent NMR and thermal Hall conductivity experiments on α-RuCl 3 demonstrate th...

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Theory of the field-revealed Kitaev spin liquid

Cited by 135 publications

References 46 publications

Giant anisotropy of Gilbert damping in a Rashba honeycomb antiferromagnet

Giant anisotropy of Gilbert damping in a Rashba honeycomb antiferromagnet

Dynamical and thermal magnetic properties of the Kitaev spin liquid candidate α-RuCl3

Magnetic field-induced intermediate quantum spin liquid with a spinon Fermi surface

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