Low-temperature properties in the bilayer Kitaev model

Tomishige, Hiroyuki; Nasu, Joji; Koga, Akihisa

doi:10.1103/physrevb.99.174424

Cited by 17 publications

(17 citation statements)

References 33 publications

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“…We have discussed the effect of the randomness in the flux configuration to clarify that power law behavior appears in the Majorana correlations. It is also interesting to discuss how robust Majorana correlations are in the related models such as the bilayer Kitaev model [39][40][41], Kitaev-Heisenberg model [10], and higher spin models [42][43][44][45][46][47][48].…”

Section: Discussionmentioning

confidence: 99%

Majorana correlations in the Kitaev model with ordered-flux structures

Koga,

Murakami,

Nasu

2021

Preprint

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We study the effects of the flux configurations on the emergent Majorana fermions in the S = 1/2 Kitaev model on a honeycomb lattice, where quantum spins are fractionalized into itinerant Majorana fermions and localized fluxes. A quantum spin liquid appears as the ground state of the Kitaev model in the flux-free sector, which has intensively been investigated so far. In this flux sector, the Majorana fermion system has linear dispersions and shows power law behavior in the Majorana correlations. On the other hand, periodically-arranged flux configurations yield low-energy excitations in the Majorana fermion system, which are distinctly different from those in the flux-free state. We find that one of the periodically arranged flux states results in the gapped Majorana dispersion and the exponential decay in the Majorana correlations. The Kitaev system with another flux configuration exhibits a semi-Dirac like dispersion, leading to the power law decay with a smaller power than that in the flux-free sector along symmetry axes. We also examine the effect of the randomness in the flux configurations and clarify that the Majorana density of states is filled by increasing the flux density, and power-law decay in the Majorana correlations remains. The present results could be important to control the motion of Majorana fermions, which carries the spin excitations, in the Kitaev candidate materials.

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Section: Discussionmentioning

confidence: 99%

Majorana correlations in the Kitaev model with ordered-flux structures

Koga,

Murakami,

Nasu

2021

Preprint

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“…As in the Kitaev model, these peculiar features of spin correlations follow from the symmetry properties of the model -an extensive number of conserved Z 2 quantities that decompose the Hilbert space into subspaces with fixed bond-parity configurations. We have also shown that the model can be mapped to a bilayer version of Kitaev model, but with some additional terms in the interlayer couplings which act to suppress gas-to-liquid phase transition in a bilayer Kitaev model [18][19][20]. Exact diagonalization of the model in 1D-zigzag chain as well as on honeycomb lattice show that the lowest energy excitations are in the spin sector (and always gapped).…”

Section: Discussionmentioning

confidence: 99%

“…For instance, we observe that the model has an extensive number of conserved quantities, magnetic correlations are highly anisotropic and confined to nearest-neighbor sites. We also find that the model is closely related to the bilayer spin-1/2 Kitaev model [18][19][20]. However, unlike the Kitaev spin-liquid arXiv:1910.00074v2 [cond-mat.str-el] 18 Dec 2019 with emergent non-local excitations, the ground state of the model is a strongly correlated paramagnet smoothly connected to the non-interacting triplon gas, and the lowest excitations are of a single-triplon character at any strength of the exchange interactions.…”

Section: Introductionmentioning

confidence: 99%

Highly frustrated magnetism in relativistic d4 Mott insulators: Bosonic analog of the Kitaev honeycomb model

Chaloupka

Khaliullin

2019

Phys. Rev. B

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We study the orbitally frustrated singlet-triplet models that emerge in the context of spin-orbit coupled Mott insulators with t 4 2g electronic configuration. In these compounds, low-energy magnetic degrees of freedom can be cast in terms of three-flavor "triplon" operators describing the transitions between spin-orbit entangled J = 0 ionic ground state and excited J = 1 levels. In contrast to a conventional, flavor-isotropic O(3) singlet-triplet models, spin-orbit entangled triplon interactions are flavor-and-bond selective and thus highly frustrated. In a honeycomb lattice, we find close analogies with the Kitaev spin model -an infinite number of conserved quantities, no magnetic condensation, and spin correlations being strictly short-ranged. However, due to the bosonic nature of triplons, there are no emergent gapless excitations within the spin gap, and the ground state is a strongly correlated paramagnet of dense triplon pairs with no long-range entanglement. Using exact diagonalization, we study the bosonic Kitaev model and its various extensions, which break exact symmetries of the model and allow magnetic condensation of triplons. Possible implications for magnetism of ruthenium oxides are discussed.

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“…For frustrated interdimer exchange, less research has been performed. In this context, very recently, bilayers of the Kitaev quantum magnet on the honeycomb lattice, coupled by interlayer Heisenberg exchange, have attracted significant attention [12][13][14][15]. A prime reason for this is, that in the limit of weak interlayer coupling, and instead of a local magnetic order parameter of Ginzburg-Landau type, the single layers of this magnet display a quantum spin liquid (QSL) state.…”

Section: Introductionmentioning

confidence: 99%

Two-triplon excitations of the Kitaev-Heisenberg-Bilayer

Wagner,

Brenig

2021

Preprint

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We study the spectrum of a bilayer of Kitaev magnets on the honeycomb lattice, coupled by Heisenberg exchange in the quantum-dimer phase at strong interlayer coupling. Using the perturbative Continuous Unitary Transformation (pCUT) we perform series expansion starting from the fully dimerized limit, to evaluate the elementary excitations, reaching up to and focusing on the two-triplon sector. In stark contrast to conventional bilayer quantum magnets, and because of the broken SU (2)-invariance, encoded in the intralayer directional compass-exchange, the bilayer Kitaev magnet is shown to exhibit a rich structure of two-triplon scattering-state continua, as well as several collective two-triplon (anti)bound states. Direct physical pictures for the occurrence of the latter are provided and the (anti)bound states are studied versus the stacking type, the spin components, and the exchange parameters. In addition to the two-triplon spectra, we investigate a corresponding experimental probe by evaluating the magnetic Raman-scattering intensity. We find a very strong sensitivity of this intensity on the two-triplon interactions and the scattering geometry, however a signal from the (anti)bound states appears only in very close proximity to the continuum.

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Low-temperature properties in the bilayer Kitaev model

Cited by 17 publications

References 33 publications

Majorana correlations in the Kitaev model with ordered-flux structures

Majorana correlations in the Kitaev model with ordered-flux structures

Highly frustrated magnetism in relativistic d4 Mott insulators: Bosonic analog of the Kitaev honeycomb model

Two-triplon excitations of the Kitaev-Heisenberg-Bilayer

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