<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>J</mml:mi><mml:mi>eff</mml:mi></mml:msub></mml:math>Description of the Honeycomb Mott Insulator<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>α</mml:mi><mml:mtext>−</mml:mtext><mml:msub><mml:mrow><mml:mi>RuCl</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Koitzsch, A.; Habenicht, Carsten; Muller, Eric A.; Knupfer, M.; Büchner, B.; Kandpal, H.C.; Brink, Jeroen van den; Nowak, Domenic; Isaeva, Anna; Doert, Th.

doi:10.1103/physrevlett.117.126403

Cited by 110 publications

(122 citation statements)

References 33 publications

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“…Compared to the Ru 4 d bands, the Cl 3 p bands are highly dispersive. Overall, our ARPES spectra are consistent with recently reported ARPES results1822. Note that the energy differences between the five Ru t 2g bands (<0.2 eV) are much smaller than the band gap (>1.2 eV).…”

Section: Resultssupporting

confidence: 92%

“…In Figs 1(d) and 2, a sharp nondispersive peak that cannot be explained by the calculations is observed at approximately −2.5 eV. The orbital character of this peak appears to be Ru 4 d because its intensity change with varied photon energies is similar to those of the main Ru t 2g bands22. Moreover, the clear separation between the Ru 4 d and the Cl 3 p bands in the ARPES spectrum cannot be reproduced in the calculations.…”

Section: Resultsmentioning

confidence: 84%

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Electronic Structure of the Kitaev Material α-RuCl3 Probed by Photoemission and Inverse Photoemission Spectroscopies

Sinn

Kim

et al. 2016

Sci Rep

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Recently, α-RuCl3 has attracted much attention as a possible material to realize the honeycomb Kitaev model of a quantum-spin-liquid state. Although the magnetic properties of α-RuCl3 have been extensively studied, its electronic structure, which is strongly related to its Kitaev physics, is poorly understood. Here, the electronic structure of α-RuCl3 was investigated by photoemission (PE) and inverse-photoemission (IPE) spectroscopies. The band gap was directly measured from the PE and IPE spectra and was found to be 1.9 eV, much larger than previously estimated values. Local density approximation (LDA) calculations showed that the on-site Coulomb interaction U could open the band gap without spin-orbit coupling (SOC). However, the SOC should also be incorporated to reproduce the proper gap size, indicating that the interplay between U and SOC plays an essential role. Several features of the PE and IPE spectra could not be explained by the results of LDA calculations. To explain such discrepancies, we performed configuration-interaction calculations for a RuCl63− cluster. The experimental data and calculations demonstrated that the 4d compound α-RuCl3 is a Jeff = 1/2 Mott insulator rather than a quasimolecular-orbital insulator. Our study also provides important physical parameters required for verifying the proposed Kitaev physics in α-RuCl3.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 84%

Electronic Structure of the Kitaev Material α-RuCl3 Probed by Photoemission and Inverse Photoemission Spectroscopies

Sinn

Kim

et al. 2016

Sci Rep

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“…Single crystals of α-RuCl 3 were prepared using high-temperature vapor-transport techniques from pure α-RuCl 3 powder with no additional transport agent. Crystals grown by an identical method have been extensively characterized via bulk and neutron scattering techniques39,42,63 revealing behavior consistent with what is expected for a relativistic Mott insulator with a large Kitaev interaction16,24,25,29,30,32,33,41,43,45,65,67,68 . The crystals have been shown to consistently exhibit a single dominant magnetic phase at low tempera-…”

mentioning

confidence: 58%

The range of non-Kitaev terms and fractional particles in α-RuCl3

Wang

Osterhoudt

Tian³

et al. 2020

npj Quantum Mater.

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Significant efforts have focused on the magnetic excitations of relativistic Mott insulators, predicted to realize the Kitaev quantum spin liquid (QSL). This exactly solvable model involves a highly entangled state resulting from bond-dependent Ising interactions that pro-1 arXiv:2003.09274v1 [cond-mat.str-el] 18 Mar 2020 duce excitations which are non-local in terms of spin flips. A key challenge in real materials is identifying the relative size of the non-Kitaev terms and their role in the emergence or suppression of fractional excitations. Here, we identify the energy and temperature boundaries of non-Kitaev interactions by direct comparison of the Raman susceptibility of α-RuCl 3 with quantum Monte Carlo (QMC) results for the Kitaev QSLs. Moreover, we further confirm the fractional nature of the magnetic excitations, which is given by creating a pair of fermionic quasiparticles. Interestingly, this fermionic response remains valid in the non-Kitaev range. Our results and focus on the use of the Raman susceptibility provide a stringent new test for future theoretical and experimental studies of QSLs. Exotic excitations with fractional quantum numbers are a key characteristic of QSLs 1-4 , which result from the long range entanglement of these non-trivial topological phases 5-7 . Originating from frustrated magnetic interactions, the fractional nature inspires an overarching goal of studying QSLs, realizing topological quantum computing immune to decoherence, with high operating temperatures from large exchange interactions 8, 9 . The last decade has seen great progress towards identifying the fractional excitations of QSLs 10-18 . Attention has focused on relativistic Mott insulators that are close to the exactly solvable Kitaev model with a QSL ground state. In materials such as A 2 IrO 3 (A = Cu, Li or Na) 4, 8, 19-23 and α-RuCl 3 24-27 , the large spin-orbit coupling and Coulomb repulsion result in j ef f = 1/2 moments on a honeycomb lattice 2, 9, 28-35 .According to the pure Kiteav model, in these materials spin flips could produce Z 2 gauge fluxes and dispersive Majorana fermions. 14, 36 .

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“…Here, we report a sizeable thermal Hall effect for α-RuCl 3 . In this compound, strong spin-orbit coupling and an edge-sharing configuration of RuCl 6 octahedra yield a honeycomb lattice of j eff = 1/2 states with dominant Kitaev interaction [8,[28][29][30]. Long-range magnetic order at T N ≈ 7 K occurs in as-grown samples of α-RuCl 3 without stacking faults, whereas stacking disorder causes a spread of the ordering temperature to up to about 14 K [31][32][33].…”

mentioning

confidence: 97%

Large thermal Hall effect in α−RuCl3 : Evidence for heat transport by Kitaev-Heisenberg paramagnons

et al. 2019

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The honeycomb Kitaev model in a magnetic field is a source of a topological quantum spin liquid with Majorana fermions and gauge flux excitations as fractional quasiparticles. We present experimental results for the thermal Hall effect of the material α-RuCl3 which recently emerged as a prime candidate for realizing such physics. At temperatures above long-range magnetic ordering T TN ≈ 8 K, we observe with an applied magnetic field B perpendicular to the honeycomb layers a sizeable positive transversal heat conductivity κxy which increases linearly with B. Upon raising the temperature, κxy(T ) increases strongly, exhibits a broad maximum at around 30 K, and eventually becomes negligible at T 125 K. Remarkably, the longitudinal heat conductivity κxx(T ) exhibits a sizeable positive thermal magnetoresistance effect. Thus, our findings provide clear-cut evidence for longitudinal and transverse magnetic heat transport and underpin the unconventional nature of the quasiparticles in the paramagnetic phase of α-RuCl3.About ten years ago, Kitaev proposed a new type of quantum spin model whose ground state has been exactly shown to be a realization of a gapless quantum spin-liquid (QSL) [1]. This is a peculiar state of matter where magnetic long-range order is suppressed due to substantial quantum fluctuations even at zero temperature [2][3][4]. In the presence of certain time-reversalsymmetry breaking perturbations, e.g. external magnetic fields, this spin liquid opens a gap, leading to a topologically non-trivial spin liquid (TQSL). The striking feature of Kitaev's TQSL is, that in addition to its unconventional bulk excitations, which are due to fractionalization of spins into localized Z 2 gauge fluxes and itinerant Majorana fermions [1,5,6], and which are present already in the gapless state, a chiral Majorana edge mode arises in the field induced gap and the Z 2 vortices acquire non-Abelian anyonic statistics [1].When investigating possible candidate materials for realizing such exotic physics, heat conductivity experiments are considered one of the few probes to study the TQSL quasiparticle fingerprints because information on the quasiparticles' specific heat, their velocity, and their scattering is provided [7]. The magnetically frustrated honeycomb compound α-RuCl 3 has been intensively studied recently as it has been suggested to host a proximate Kitaev TQSL [8,9]. A profound understanding of how putative fractional magnetic excitations contribute to the heat transport in α-RuCl 3 is thus highly desirable.Several heat conductivity studies on α-RuCl 3 yield an inconsistent picture on possible heat transport by emergent quasiparticles of the spin system. Heat transport by itinerant spin excitation has been inferred from an anomaly in the in-plane longitudinal heat conductivity κ xx at around 100 K [10] and from a magnetic fieldinduced low-temperature enhancement of κ xx for fields B 8 T parallel to the material's honeycomb planes [11]. These interpretations however, have recently been ruled out by results for the...

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JeffDescription of the Honeycomb Mott Insulatorα−RuCl3

Cited by 110 publications

References 33 publications

Electronic Structure of the Kitaev Material α-RuCl3 Probed by Photoemission and Inverse Photoemission Spectroscopies

Electronic Structure of the Kitaev Material α-RuCl3 Probed by Photoemission and Inverse Photoemission Spectroscopies

The range of non-Kitaev terms and fractional particles in α-RuCl3

Large thermal Hall effect in α−RuCl3 : Evidence for heat transport by Kitaev-Heisenberg paramagnons

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