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Title: Kondo route to spin inhomogeneities in the honeycomb Kitaev model

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Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 2; Related Information: CHORUS Timestamp: 2016-07-08 18:10:42; Journal ID: ISSN 2469-9950
American Physical Society
Country of Publication:
United States

Citation Formats

Das, S. D., Dhochak, K., and Tripathi, V. Kondo route to spin inhomogeneities in the honeycomb Kitaev model. United States: N. p., 2016. Web. doi:10.1103/PhysRevB.94.024411.
Das, S. D., Dhochak, K., & Tripathi, V. Kondo route to spin inhomogeneities in the honeycomb Kitaev model. United States. doi:10.1103/PhysRevB.94.024411.
Das, S. D., Dhochak, K., and Tripathi, V. Fri . "Kondo route to spin inhomogeneities in the honeycomb Kitaev model". United States. doi:10.1103/PhysRevB.94.024411.
title = {Kondo route to spin inhomogeneities in the honeycomb Kitaev model},
author = {Das, S. D. and Dhochak, K. and Tripathi, V.},
abstractNote = {},
doi = {10.1103/PhysRevB.94.024411},
journal = {Physical Review B},
number = 2,
volume = 94,
place = {United States},
year = {Fri Jul 08 00:00:00 EDT 2016},
month = {Fri Jul 08 00:00:00 EDT 2016}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevB.94.024411

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  • Paramagnetic impurities in a quantum spin liquid give rise to Kondo effects with highly unusual properties. We have studied the effect of locally coupling a paramagnetic impurity with the spin-1/2 honeycomb Kitaev model in its gapless spin-liquid phase. The ( impurity) scaling equations are found to be insensitive to the sign of the coupling. The weak and strong coupling fixed points are stable, with the latter corresponding to a noninteracting vacancy and an interacting, spin-1 defect for the antiferromagnetic and ferromagnetic cases, respectively. The ground state in the strong coupling limit in both cases has a nontrivial topology associated withmore » a finite Z(2) flux at the impurity site. For the antiferromagnetic case, this result has been obtained straightforwardly owing to the integrability of the Kitaev model with a vacancy. The strong-coupling limit of the ferromagnetic case is, however, nonintegrable, and we address this problem through exact-diagonalization calculations with finite Kitaev fragments. Our exact diagonalization calculations indicate that the weak-to-strong coupling transition and the topological phase transition occur rather close to each other and are possibly coincident. We also find an intriguing similarity between the magnetic response of the defect and the impurity susceptibility in the two-channel Kondo problem.« less
  • We consider the quasi-two-dimensional pseudo-spin-1/2 Kitaev–Heisenberg model proposed for A{sub 2}IrO{sub 3} (A = Li, Na) compounds. The spin-wave excitation spectrum, the sublattice magnetization, and the transition temperatures are calculated in the random phase approximation for four different ordered phases observed in the parameter space of the model: antiferromagnetic, stripe, ferromagnetic, and zigzag phases. The Néel temperature and temperature dependence of the sublattice magnetization are compared with the experimental data on Na{sub 2}IrO{sub 3}.
  • Quantum spin liquids (QSLs) are topological states of matter exhibiting remarkable properties such as the capacity to protect quantum information from decoherence. While their featureless ground states have precluded their straightforward experimental identification, excited states are more revealing and particularly interesting due to the emergence of fundamentally new excitations such as Majorana Fermions. Ideal probes of these excitations are inelastic neutron scattering experiments. We report these here for a ruthenium-based material α-RuCl 3, continuing a major search (so far concentrated on iridium materials inimical to neutron probes) for realizations of the celebrated Kitaev honeycomb topological QSL. Our measurements confirm themore » requisite strong spin-orbit coupling and low-temperature magnetic order matching predictions proximate to the QSL. We find stacking faults, inherent to the highly 2D nature of the material, resolve an outstanding puzzle. Crucially, dynamical response measurements above interlayer energy scales are naturally accounted for in terms of deconfinement physics expected for QSLs. Comparing these with recent dynamical calculations involving gauge flux excitations and Majorana fermions of the pure Kitaev model, we propose the excitation spectrum of α-RuCl 3 as prime candidate for realization of fractionalized Kitaev physics.« less
  • Combining thermodynamic measurements with theoretical calculations we demonstrate that the iridates A{sub 2}IrO{sub 3} (A = Na, Li) are magnetically ordered Mott insulators where the magnetism of the effective spin-orbital S = 1/2 moments can be captured by a Heisenberg-Kitaev (HK) model with interactions beyond nearest-neighbor exchange. Experimentally, we observe an increase of the Curie-Weiss temperature from {Theta} {approx} -125 K for Na{sub 2}IrO{sub 3} to {Theta} {approx} -33 K for Li{sub 2}IrO{sub 3}, while the ordering temperature remains roughly the same T{sub N} {approx} 15 K. Using functional renormalization group calculations we show that this evolution of {Theta} andmore » T{sub N} as well as the low temperature zigzag magnetic order can be captured within this extended HK model. We estimate that Na{sub 2}IrO{sub 3} is deep in a magnetically ordered regime, while Li{sub 2}IrO{sub 3} appears to be close to a spin-liquid regime.« less