Probing 
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 Beyond Magnetic Order: Effects of Temperature and Magnetic Field

Winter, Stephen M.; Riedl, Kira; Kaib, David A. S.; Coldea, R.; Valentí, Roser

doi:10.1103/physrevlett.120.077203

Cited by 160 publications

(169 citation statements)

References 66 publications

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“…This may also help to constrain the possible values of J 2 [79] and anisotropic exchanges, although exchange disorder may be very efficient at suppressing these features [80]. Because of their nonspin-conserving nature, dominant pseudodipolar interactions should manifest as an asymptotic approach to saturated magnetization, as recently observed in the candidate Kitaev spin liquid α-RuCl 3 [81]. Finally, we note that the role and extent of CEF and exchange disorder remains an outstanding issue in YbMgGaO 4 with possible impact ranging from the mimicry of a spin liquid [47,48,82,83] to disorder-induced entanglement [84][85][86].…”

Section: Discussionmentioning

confidence: 93%

Hierarchy of Exchange Interactions in the Triangular-Lattice Spin Liquid YbMgGaO4

et al. 2018

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The spin-1=2 triangular lattice antiferromagnet YbMgGaO 4 has attracted attention recently as a quantum spin-liquid candidate with the possible presence of off-diagonal anisotropic exchange interactions induced by spin-orbit coupling. Whether a quantum spin liquid is stabilized or not depends on the interplay of various exchange interactions with chemical disorder that is inherent to the layered structure of the compound. We combine time-domain terahertz spectroscopy and inelastic neutron scattering measurements in the field-polarized state of YbMgGaO 4 to obtain better insight of its exchange interactions. Terahertz spectroscopy in this fashion functions as a high-field electron spin resonance and probes the spin-wave excitations at the Brillouin zone center, ideally complementing neutron scattering. A global spin-wave fit to all our spectroscopic data at fields over 4 T, informed by the analysis of the terahertz spectroscopy linewidths, yields constraints on the disorder-averaged g factors and exchange interactions. Our results paint YbMgGaO 4 as an easy-plane XXZ antiferromagnet with the combined and necessary presence of subleading next-nearest neighbor and weak anisotropic off-diagonal nearest-neighbor interactions. Moreover, the obtained g factors are substantially different from previous reports. This work establishes the hierarchy of exchange interactions in YbMgGaO 4 from high-field data alone and thus strongly constrains possible mechanisms responsible for the observed spin-liquid phenomenology.

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Section: Discussionmentioning

confidence: 93%

Hierarchy of Exchange Interactions in the Triangular-Lattice Spin Liquid YbMgGaO4

et al. 2018

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“…This observation leads us to conclude that the two resonances are distinct excitations of the underlying zigzag AF order of α-RuCl 3 with a single T N of 7 K. Moreover, the presence of both modes above T N (see Fig. S2 of the Supplemental Material [52]), but with smaller amplitude, suggests the persistence of shortrange spin correlations in the paramagnetic state above the ordering temperature [27,55].…”

Section: B Assignment Of the Resonancesmentioning

confidence: 88%

Magnetic field-dependent low-energy magnon dynamics in α–RuCl3

et al. 2019

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Revealing the spin excitations of complex quantum magnets is key to developing a minimal model that explains the underlying magnetic correlations in the ground state. We investigate the lowenergy magnons in α-RuCl3 by combining time-domain terahertz spectroscopy under an external magnetic field and model Hamiltonian calculations. We observe two absorption peaks around 2.0 and 2.4 meV, which we attribute to zone-center spin waves. Using linear spin-wave theory with only nearest-neighbor terms of the exchange couplings, we calculate the antiferromagnetic resonance frequencies and reveal their dependence on an external field applied parallel to the nearest-neighbor Ru-Ru bonds. We find that the magnon behavior in an applied magnetic field can be understood only by including an off-diagonal Γ exchange term to the minimal Heisenberg-Kitaev model. Such an anisotropic exchange interaction that manifests itself as a result of strong spin-orbit coupling can naturally account for the observed mixing of the modes at higher fields strengths. arXiv:1909.00462v1 [cond-mat.str-el] 1 Sep 2019

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“…Indeed, Raman scattering was the first to reveal the continuum from magnetic excitations in α-RuCl 3 11 . However, a careful study of the Kitaev term's temperature and energy dependence is still a challenge, as one requires a very high temperature and energy resolution to show the spectral change and directly compare the spectra with theoretical calculations 54 . Previously, Raman efforts relied on spectral integration over a certain energy range which averaged out the energy dependence of the excitations, and, the low scattering intensity made it difficult to directly compare the spectra with theoretical calculations from the exact Kitaev model.…”

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confidence: 99%

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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Probing α−RuCl3 Beyond Magnetic Order: Effects of Temperature and Magnetic Field

Cited by 160 publications

References 66 publications

Hierarchy of Exchange Interactions in the Triangular-Lattice Spin Liquid YbMgGaO4

Hierarchy of Exchange Interactions in the Triangular-Lattice Spin Liquid YbMgGaO4

Magnetic field-dependent low-energy magnon dynamics in α–RuCl3

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

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