Large field-induced gap of Kitaev-Heisenberg paramagnons in $α$-RuCl$_{3}$

Hentrich, Richard; Wolter, Anja U. B.; Zotos, Xenophon; Brenig, Wolfram; Nowak, Domenic; Isaeva, Anna; Doert, Thomas; Banerjee, Arnab; Lampen-Kelley, Paula; Mandrus, David G.; Nagler, Stephen E.; Sears, Jennifer; Kim, Young-June; Büchner, Bernd; Hess, Christian

doi:10.48550/arxiv.1703.08623

Cited by 17 publications

(40 citation statements)

References 43 publications

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“…We have also found that application of magnetic field h to a model, perturbed by DM interaction, produces the gap ∆ ∼ Dh/K in the Majorana fermion spectrum, rendering decay of spin correlations in space and time exponential. Note in this respect that linear growth of the spin-liquid excitation gap has been recently observed 28,29 in α-RuCl 3 .…”

Section: Introductionsupporting

confidence: 53%

Perturbed Kitaev model: Excitation spectrum and long-ranged spin correlations

Lunkin

Tikhonov

Фейгельман

2019

Journal of Physics and Chemistry of Solids

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We developed general approach to the calculation of power-law infrared asymptotics of spin-spin correlation functions in the Kitaev honeycomb model with different types of perturbations. We have shown that in order to find these correlation functions, one can perform averaging of some bilinear forms composed out of free Majorana fermions, and we presented the method for explicit calculation of these fermionic densities. We demonstrated how to derive an effective Hamiltonian for the Majorana fermions, including the effects of perturbations. For specific application of the general theory, we have studied the effect of the Dzyaloshinskii-Moriya anisotropic spin-spin interaction; we demonstrated that it leads, already in the second order over its relative magnitude D/K, to a power-law spin correlation functions, and calculated dynamical spin structure factor of the system. We have shown that an external magnetic field h in presence of the DM interaction, opens a gap in the excitation spectrum of magnitude ∆ ∝ Dh.

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Section: Introductionsupporting

confidence: 53%

Perturbed Kitaev model: Excitation spectrum and long-ranged spin correlations

Lunkin

Tikhonov

Фейгельман

2019

Journal of Physics and Chemistry of Solids

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“…A suitable perturbation that allows to stabilize the spin-liquid state experimentally is therefore much soughtafter. 13 Interestingly, in α-RuCl 3 a number of very recent measurements indeed appear to be consistent with a, possibly continuous, 14 transition from the ordered phase towards a quantum paramagnetic phase, driven by magnetic field [15][16][17][18][19][20] or external pressure. 21,22 At zero field and ambient pressure, magnetic order must be caused by interactions beyond the nearestneighbor Kitaev model, 5 and it has been pointed out that longer-range 23 as well as off-diagonal interactions 24 may play a role.…”

Section: Introductionmentioning

confidence: 69%

“…Recent experiments report a field-induced transition in α-RuCl 3 from a canted ordered phase into a putative quantum disordered phase when a field of around 7 T (10 T) is applied along an in-plane 15,[17][18][19][20] (intermediate 16 ) direction. While at least one, 14 or more, 20 field-induced phase transitions appear to be observable independent of the specific sample, the nature of the adjacent phases has so far not been established beyond doubt.…”

Section: B Field-induced Transitionsmentioning

confidence: 99%

Magnetization processes of zigzag states on the honeycomb lattice: Identifying spin models for α−RuCl3 and Na2IrO3

2017

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We study the field-induced magnetization processes of extended Heisenberg-Kitaev models on the honeycomb lattice, taking into account off-diagonal and longer-range exchange interactions, using a combination of Monte-Carlo simulations, classical energy minimization, and spin-wave theory. We consider a number of different parameter sets, previously proposed to describe the magnetic behavior of α-RuCl3 and Na2IrO3 with their antiferromagnetic zigzag ground states. By classifying these parameter sets, we reveal the existence of three distinct mechanisms to stabilize zigzag states, which differ in the sign of the nearest-neighbor Kitaev interaction, the role of longer-range interactions, and the magnitude of the off-diagonal Γ1 interaction. While experimentally hardly distinguishable at zero field, we find that the three different scenarios lead to significantly different magnetization processes in applied magnetic fields. In particular, we show that a sizable off-diagonal interaction Γ1 > 0 naturally explains the strongly anisotropic field responses observed in α-RuCl3 without the need for a strong anisotropy in the effective g tensor. Moreover, for a generic field direction, it leads to a high-field state with a finite transversal magnetization, which should be observable in α-RuCl3. Scenario 1: If the most dominant interactions are between nearest neighbors only, a zigzag-ordered state occurs if the Kitaev interaction is antiferromagnetic, K 1 > 0. 30 Scenario 2: Zigzag order can be stabilized also for ferromagnetic Kitaev coupling, K 1 < 0, if a sizable arXiv:1706.05380v2 [cond-mat.str-el] 1 Sep 2017

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“…On this basis, precursors of the Kitaev QSL have been investigated in these materials, e.g., by the neutron and Raman scattering measurements [10,11], in comparison with the theoretical calculations [12][13][14][15][16][17]. Very recently, some attempts have been made to grasp the itinerant nature of the Majorana fermions by measuring the thermal conductivity [18][19][20]. While theoretical works have been done for the thermal transport in one-dimensional Kitaev systems [21,22] and that car-ried by magnons in magnetically ordered states in the Kitaev-Heisenberg model [23], the thermal conductivity owing to the Majorana fermions emergent in the two-dimensional Kitaev QSL remains unclear.…”

mentioning

confidence: 99%

Thermal Transport in the Kitaev Model

2017

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In conventional insulating magnets, heat is carried by magnons and phonons. In contrast, when the magnets harbor a quantum spin liquid state, emergent quasiparticles from the fractionalization of quantum spins can carry heat. Here, we investigate unconventional thermal transport yielded by such exotic carriers, in both longitudinal and transverse components, for the Kitaev model, whose ground state is exactly shown to be a quantum spin liquid with fractional excitations described as itinerant Majorana fermions and localized Z_{2} fluxes. We find that the longitudinal thermal conductivity exhibits a single peak at a high temperature, while the nonzero frequency component has a peak at a low temperature, reflecting the spin fractionalization. On the other hand, we show that the transverse thermal conductivity is induced by the magnetic field in a wide temperature range up to the energy scale of the bare exchange coupling; while increasing temperature, the transverse response divided by temperature decreases from the quantized value expected for the topologically nontrivial ground state and shows nonmonotonic temperature dependence. These characteristic behaviors provide experimentally accessible evidence of fractional excitations in the proximity to the Kitaev quantum spin liquid.

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Large field-induced gap of Kitaev-Heisenberg paramagnons in $α$-RuCl$_{3}$

Cited by 17 publications

References 43 publications

Perturbed Kitaev model: Excitation spectrum and long-ranged spin correlations

Perturbed Kitaev model: Excitation spectrum and long-ranged spin correlations

Magnetization processes of zigzag states on the honeycomb lattice: Identifying spin models for α−RuCl3 and Na2IrO3

Thermal Transport in the Kitaev Model

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