Angle-resolved photoemission study of the Kitaev candidate<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>α</mml:mi><mml:mo>−</mml:mo><mml:msub><mml:mi>RuCl</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

Zhou, Xiaoqing; Li, Haoxiang; Waugh, Justin; Parham, Stephen; Kim, Heung Sik; Sears, Jennifer; Gomes, Abel; Kee, Hae‐Young; Kim, Yong Baek; Dessau, D. S.

doi:10.1103/physrevb.94.161106

Cited by 67 publications

(58 citation statements)

References 35 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%

“…We estimate the band gap of α -RuCl 3 to be 1.9 eV, which is much larger than the values reported in earlier studies15161718. In principle, the size of the band gap should correspond to the energy range of zero intensity in PE and IPE spectra.…”

Section: Resultscontrasting

confidence: 51%

“…Optical studies found an optical gap of 0.2 eV16 that was later revised to 1.0 eV17. Recently, an angle-resolved photoemission spectroscopy (ARPES) study showed that the Fermi level E F is located 1.2 eV above the valence band maximum, suggesting that the band gap should be larger than 1.2 eV18. There are two possible insulating mechanisms for a spin-orbit-coupled t 2g 5 honeycomb system19: A J eff = 1/2 Mott insulator20 and a quasimolecular-orbital band insulator21.…”

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confidence: 99%

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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: Resultscontrasting

confidence: 51%

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confidence: 99%

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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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“…4c) is much smaller than the gap of ≈1.2 eV observed in recent ARPES measurements39, which was also explained as the correlation induced Mott gap. On the other hand, the presence of ≈0.25 eV gap in the STS experiment agrees well with observations of a peak at about 0.3 eV in X-ray adsorption measurements1740 and of a 0.2 eV gap in neutron measurements of bulk α-RuCl 3 crystals3.…”

Section: Resultssupporting

confidence: 48%

Atomic-scale observation of structural and electronic orders in the layered compound α-RuCl3

et al. 2016

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A pseudospin-1/2 Mott phase on a honeycomb lattice is proposed to host the celebrated two-dimensional Kitaev model which has an elusive quantum spin liquid ground state, and fascinating physics relevant to the development of future templates towards topological quantum bits. Here we report a comprehensive, atomically resolved real-space study by scanning transmission electron and scanning tunnelling microscopies on a novel layered material displaying Kitaev physics, α-RuCl3. Our local crystallography analysis reveals considerable variations in the geometry of the ligand sublattice in thin films of α-RuCl3 that opens a way to realization of a spatially inhomogeneous magnetic ground state at the nanometre length scale. Using scanning tunnelling techniques, we observe the electronic energy gap of ≈0.25 eV and intra-unit cell symmetry breaking of charge distribution in individual α-RuCl3 surface layer. The corresponding charge-ordered pattern has a fine structure associated with two different types of charge disproportionation at Cl-terminated surface.

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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-…”

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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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Angle-resolved photoemission study of the Kitaev candidateα−RuCl3

Cited by 67 publications

References 35 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

Atomic-scale observation of structural and electronic orders in the layered compound α-RuCl3

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

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