Observation of two types of fractional excitation in the Kitaev honeycomb magnet

Janša, N.; Zorko, A.; Gomilšek, M.; Pregelj, M.; Krämer, Karl; Biner, Daniel; Biffin, Alun; Rüegg, Christian; Klanjšek, M.

doi:10.1038/s41567-018-0129-5

Cited by 165 publications

(133 citation statements)

References 54 publications

Supporting

Mentioning

124

Contrasting

Order By: Relevance

“…In this context, it is also interesting to compare our results with those previously reported for α-RuCl 3 [50][51][52], because magnons also dominate its spin excitation spectrum in the low-field regime [19][20][21]. Not surprisingly, 1=T 1 observed at the 35 Cl site of α-RuCl 3 in the low-field regime B ext ¼ 2.35 T with antiferromagnetic ground state [52] is similar to the conventional behavior observed here for Na 2 IrO 3 . Our NQR results for Cu 2 IrO 3 in Figs.…”

Section: Inverse Laplace Transform Of Mðtþ For Direct Estimation Osupporting

confidence: 86%

Spin Excitations of a Proximate Kitaev Quantum Spin Liquid Realized in Cu2IrO3

et al. 2019

View full text Add to dashboard Cite

Magnetic moments arranged at the corners of a honeycomb lattice are predicted to form a novel state of matter, the Kitaev quantum spin liquid, under the influence of frustration effects between bond-dependent Ising interactions. Some layered honeycomb iridates and related materials, such as Na 2 IrO 3 and α-RuCl 3 , are proximate to the Kitaev quantum spin liquid, but bosonic spin-wave excitations associated with undesirable antiferromagnetic long-range order mask the inherent properties of the Kitaev Hamiltonian. Here, we use 63 Cu nuclear quadrupole resonance to uncover the low-energy spin excitations in the nearly ideal honeycomb lattice of effective spin S ¼ 1=2 at the Ir 4þ sites in Cu 2 IrO 3 . We demonstrate that, unlike Na 2 IrO 3 , Ir spin fluctuations exhibit no evidence for critical slowing-down toward magnetic long-range order in zero external magnetic field. Moreover, the low-energy spin excitation spectrum is dominated by a mode that has a large excitation gap comparable to the Ising interactions, a signature expected for Majorana fermions of the Kitaev quantum spin liquid.

show abstract

Section: Inverse Laplace Transform Of Mðtþ For Direct Estimation Osupporting

confidence: 86%

Spin Excitations of a Proximate Kitaev Quantum Spin Liquid Realized in Cu2IrO3

et al. 2019

View full text Add to dashboard Cite

show abstract

“…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: 57%

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

Wang

Osterhoudt

Tian³

et al. 2020

npj Quantum Mater.

View full text Add to dashboard Cite

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 .

show abstract

“…In this context, organics such as κ-(BEDT-TTF) 2 Cu 2 (CN) 3 [20] and EtMe 3 Sb[Pd(dmit) 2 ] 2 [21], the transition metal dichalcogenides 1T-TaS 2 [19] and a large family of rare-earth dichalcogenides AReX 2 (A = alkali or monovalent ions, Re = rare earth, X = O, S, Se) [22] have been explored. Remarkably, recent NMR and thermal Hall conductivity experiments on α-RuCl 3 demonstrate that one can drive the magnetically ordered phase into a QSL phase using an external mag-netic field [23,24]. To this end, various numerical tools were used to explore the possible QSL phases in the models relevant to candidate honeycomb materials with an external magnetic field [25][26][27][28][29].…”

mentioning

confidence: 99%

Magnetic field-induced intermediate quantum spin liquid with a spinon Fermi surface

Patel

Trivedi

2019

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The Kitaev model with an applied magnetic field in the H||[111] direction shows two transitions: from a non-abelian gapped quantum spin liquid (QSL) to a gapless QSL at Hc1 0.2K and a second transition at a higher field Hc2 0.35K to a gapped partially polarized phase, where K is the strength of the Kitaev exchange interaction. We identify the intermediate phase to be a gapless U(1) QSL, and determine the spin structure function S(k) and the Fermi surface S F (k) of the gapless spinons using the density matrix renormalization group (DMRG) method for large honeycomb clusters. Further calculations of static spin-spin correlations, magnetization, spin susceptibility, and finite temperature specific heat and entropy, corroborate the gapped and gapless nature of the different field-dependent phases. In the intermediate phase, the spin-spin correlations decay as a power law with distance, indicative of a gapless phase.The inspired exact solution of the Kitaev model on a twodimensional honeycomb lattice with bond dependent spin exchange interaction [1] (Eq. 1) has emerged as a paradigmatic model for quantum spin liquids (QSL). For equal bond interactions (K), the ground state of the Kitaev model is known to be a topologically non-trivial gapless QSL with fractionalized excitations. The multiple ground state degeneracy reflects the topology of the lattice manifold (2-fold degeneracy on a cylinder and 4-fold degeneracy on a torus). The promise of utilizing fractionalized excitations for applications in robust quantum computing [1][2][3][4][5] has led to considerable excitement and activity in the field from diverse directions, all the way from fundamental developments to applications. Upon breaking time-reversal symmetry (TRS), for example by applying a magnetic field, the exact solvability of the Kitaev model is lost but perturbatively it can be shown that the Kitaev gapless QSL becomes a gapped QSL phase with non-abelian anyonic excitations [1].In order to realize the exotic properties of the Kitaev model, there has been keen interest to discover Kitaev physics in materials. To this end, Mott insulators with magnetic frustration and large spin-orbit coupling have been proposed [6], leading to the discovery of α-RuCl 3 and A 2 IrO 3 (A = Na, Li). These are candidate QSL materials with the desired honeycomb geometry. Although given additional interactions beyond the Kitaev interaction in materials, there is still controversy about the regimes where Kitaev physics can be accessed [7][8][9][10][11][12]. Additionally, triangular and Kagome lattice with spin frustration has also been proposed as a candidate for a QSL [13][14][15][16][17][18][19]. In this context, organics such as κ-(BEDT-TTF) 2 Cu 2 (CN) 3 [20] and EtMe 3 Sb[Pd(dmit) 2 ] 2 [21], the transition metal dichalcogenides 1T-TaS 2 [19] and a large family of rare-earth dichalcogenides AReX 2 (A = alkali or monovalent ions, Re = rare earth, X = O, S, Se) [22] have been explored. Remarkably, recent NMR and thermal Hall conductivity experiments on α-RuCl 3 demonstrate th...

show abstract

Observation of two types of fractional excitation in the Kitaev honeycomb magnet

Cited by 165 publications

References 54 publications

Spin Excitations of a Proximate Kitaev Quantum Spin Liquid Realized in Cu2IrO3

Spin Excitations of a Proximate Kitaev Quantum Spin Liquid Realized in Cu2IrO3

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

Magnetic field-induced intermediate quantum spin liquid with a spinon Fermi surface

Contact Info

Product

Resources

About