Muon Spin Relaxation Evidence for the U(1) Quantum Spin-Liquid Ground State in the Triangular Antiferromagnet<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>YbMgGaO</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Li, Yuesheng; Adroja, D. T.; Biswas⃰, Pabitra Kumar; Baker, Peter J.; Zhang, Qian; Liu, Juanjuan; Tsirlin, Alexander A.; Gegenwart, P.; Zhang, Qingming

doi:10.1103/physrevlett.117.097201

Cited by 201 publications

(231 citation statements)

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“…The resulting ground state Kramers doublet of the Yb 3+ ion, whose two-fold degeneracy is protected by the time-reversal symmetry, is well separated from the excited doublets and is responsible for the low-temperature magnetic properties of YbMgGaO 4 . No signature of time-reversal symmetry breaking is observed for YbMgGaO 4 down to the lowest measured temperature [36][37][38] . Applying the recent theoretical result on spin-orbit-coupled Mott insulators 42 , two of us and collaborators have proposed YbMgGaO 4 to be the first QSL candidate in the spin-orbit-coupled Mott insulator with odd electron fillings [34][35][36]39 .…”

Section: +mentioning

confidence: 99%

“…At the mean time, the abundance of strongly correlated materials with 5d and 4f electrons, such as iridates and rare-earth materials 1,2 , brings a fertile arena to explore various emergent and exotic phases that arise from such an interplay . The recently discovered quantum spin liquid (QSL) candidate YbMgGaO 4 33 , where the rare-earth Yb atoms form a perfect triangular lattice, is an ideal system that involves strong spin-orbital entanglement in the strong Mott insulating regime of the Yb electrons [34][35][36][37][38][39][40][41] .…”

Section: Introductionmentioning

confidence: 99%

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Spinon Fermi surface U(1) spin liquid in the spin-orbit-coupled triangular-lattice Mott insulator YbMgGaO4

Lü

Chen

2017

Phys. Rev. B

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Motivated by the recent progress on the spin-orbit-coupled triangular lattice spin liquid candidate YbMgGaO4, we carry out a systematic projective symmetry group analysis and mean-field study of candidate U(1) spin liquid ground states. Due to the spin-orbital entanglement of the Yb moments, the space group symmetry operation transforms both the position and the orientation of the local moments, and hence brings different features for the projective realization of the lattice symmetries from the cases with spin-only moments. Among the eight U(1) spin liquids that we find with the fermionic parton construction, only one spin liquid state, that was proposed and analyzed in Yao Shen, et. al., Nature 540, 559-562 (2016) and labeled as U1A00 in the present work, stands out and gives a large spinon Fermi surface and provides a consistent explanation for the spectroscopic results in YbMgGaO4. Further connection of this spinon Fermi surface U(1) spin liquid with YbMgGaO4 and the future directions are discussed. Finally, our results may apply to other spinorbit-coupled triangular lattice spin liquid candidates, and more broadly, our general approach can be well extended to spin-orbit-coupled spin liquid candidate materials.

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Section: +mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spinon Fermi surface U(1) spin liquid in the spin-orbit-coupled triangular-lattice Mott insulator YbMgGaO4

Lü

Chen

2017

Phys. Rev. B

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“…The magnetic Yb 3þ ions carry effective spin-1=2 moments in a symmetry environment allowing anisotropic exchange interactions [41,47] in the absence of antisymmetric (Dzyaloshinsky-Moriya) terms and magnetic defects, both of which are present in other two-dimensional QSL candidates such as herbertsmithite [56][57][58]. The immediate availability of single crystals [55] uncovered a QSL phenomenology in YbMgGaO 4 characterized by the absence of spin ordering or freezing down to T ¼ 100 mK in muon spin relaxation measurements [59], much lower than the Curie-Weiss temperature θ W ≈ −4 K, and a power-law behavior for the magnetic specific heat at low temperatures [55,60]. Perhaps the strongest evidence for a QSL in YbMgGaO 4 came from inelastic neutron scattering measurements in zero field that unraveled a broad continuum of magnetic excitations across the entire Brillouin zone [61][62][63].…”

Section: Introductionmentioning

confidence: 99%

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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“…It has been argued that the spin-orbit origin of its magnetic properties and the pseudo-spin nature of the low-energy states with highly anisotropic effective spin interactions may potentially open a new route to realizing quantum spin liquids [44][45][46]. While the lack of ordering, anomalous specific heat, and especially continuum-like excitations in inelastic neutron scattering [45,47] all provide strong support to the idea of an intrinsic spin liquid, other experimental findings are increasingly at odds with this picture.…”

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confidence: 99%

Disorder-Induced Mimicry of a Spin Liquid in YbMgGaO4

et al. 2017

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We suggest that a randomization of the pseudo-dipolar interaction in the spin-orbit-generated lowenergy Hamiltonian of YbMgGaO4 due to an inhomogeneous charge environment from a natural mixing of Mg 2+ and Ga 3+ can give rise to orientational spin disorder and mimic a spin-liquid-like state. In the absence of such quenched disorder, 1/S and density matrix renormalization group calculations both show robust ordered states for the physically relevant phases of the model. Our scenario is consistent with the available experimental data and further experiments are proposed to support it.PACS numbers: 75.10. Jm, 75.40.Gb, 78.70.Nx Dating back to Wannier's pioneering study of the Ising model [1], triangular lattice models and materials with frustrating antiferromagnetic interactions have served as fertile playgrounds for new ideas [2][3][4][5][6][7][8][9][10]. These systems continue to draw significant experimental [11][12][13][14][15] and theoretical interest because they exhibit many intriguing novel ordered states [16][17][18][19][20][21][22] and unusual continuumlike spectral features [23][24][25][26][27][28][29][30][31] and especially because they provide a setting for spin-liquid states [32][33][34][35][36][37][38][39][40][41][42].Among the latest experimental discoveries [14,15], a rare-earth triangular-lattice antiferromagnet YbMgGaO 4 has recently emerged as a new candidate for a quantum spin liquid of the effective spin-1/2 degrees of freedom of Yb 3+ ions [43,44]. It has been argued that the spin-orbit origin of its magnetic properties and the pseudo-spin nature of the low-energy states with highly anisotropic effective spin interactions may potentially open a new route to realizing quantum spin liquids [44][45][46]. While the lack of ordering, anomalous specific heat, and especially continuum-like excitations in inelastic neutron scattering [45,47] all provide strong support to the idea of an intrinsic spin liquid, other experimental findings are increasingly at odds with this picture.First, in magnetization vs field measurements, there is no sharpening of the transition to the saturated phase upon lowering the temperature, and the lack of the upward curvature in M (H) at the lowest T 's [43,44] is indicative of low quantum fluctuations in the ground state [48]. Second, in the high-field polarized phase, neutron scattering shows that continuum-like excitations persist, with significant smearing of magnon lines that are expected to be sharp [47]. In addition, an apparent absence of any detectable contribution of spin excitations to thermal conductivity down to the lowest temperatures, accompanied by a strong deviation of the phonon part from the ballistic T 3 form [49], both suggest strong scattering effects. These, combined with the anomalously broadened higher-energy Yb 3+ doublet structure [47, 50] and a ubiquitous mixing of Mg 2+ and Ga 3+ ions in the non-magnetic layers [43,47], implicate disorder as a key contributor to the observed properties [50].In this Letter, we first argue that a hypothetical,...

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Muon Spin Relaxation Evidence for the U(1) Quantum Spin-Liquid Ground State in the Triangular AntiferromagnetYbMgGaO4

Cited by 201 publications

References 55 publications

Spinon Fermi surface U(1) spin liquid in the spin-orbit-coupled triangular-lattice Mott insulator YbMgGaO4

Spinon Fermi surface U(1) spin liquid in the spin-orbit-coupled triangular-lattice Mott insulator YbMgGaO4

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

Disorder-Induced Mimicry of a Spin Liquid in YbMgGaO4

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