Instabilities of spin-liquid states in a quantum kagome antiferromagnet

Gomilšek, M.; Klanjšek, M.; Pregelj, M.; Coomer, Fiona C.; Luetkens, H.; Zaharko, O.; Fennell, T.; Li, Y.; Zhang, Q. M.; Zorko, A.

doi:10.1103/physrevb.93.060405

Cited by 31 publications

(50 citation statements)

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“…They are crucial to pinpoint the different characters and scenarios of SL behavior, in particular whether materials follow gapped or gapless SL. These quantities are mostly extracted from experiments on KL systems, the prominent example being herbertsmithite [27][28][29][30][31], but also related compounds in the same class [32][33][34][35][36][37]. Another example are organic compounds where the relevant lattice is triangular [38][39][40][41] as well as charge-density-wave system 1T-TaS 2 , recently established as SL with composite S = 1/2 spins on TL [42][43][44][45].…”

Section: Introductionmentioning

confidence: 99%

Vanishing Wilson ratio as the hallmark of quantum spin-liquid models

Prelovšek

Morita

Tohyama

et al. 2020

Phys. Rev. Research

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We present numerical results for finite-temperature T > 0 thermodynamic quantities, entropy s(T ), uniform susceptibility χ0(T ) and the Wilson ratio R(T ), for several isotropic S = 1/2 extended Heisenberg models which are prototype models for planar quantum spin liquids. We consider in this context the frustrated J1-J2 model on kagome, triangular, and square lattice, as well as the Heisenberg model on triangular lattice with the ring exchange. Our analysis reveals that typically in the spin-liquid parameter regimes the low-temperature s(T ) remains considerable, while χ0(T ) is reduced consistent mostly with a triplet gap. This leads to vanishing R(T → 0), being the indication of macroscopic number of singlets lying below triplet excitations. This is in contrast to J1-J2 Heisenberg chain, where R(T → 0) either remains finite in the gapless regime, or the singlet and triplet gap are equal in the dimerized regime. arXiv:1912.00876v1 [cond-mat.str-el]

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Section: Introductionmentioning

confidence: 99%

Vanishing Wilson ratio as the hallmark of quantum spin-liquid models

Prelovšek

Morita

Tohyama

et al. 2020

Phys. Rev. Research

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“…accessible temperatures [20], three orders of magnitude below the dominant exchange interactions [21]. As revealed in our recent muon spin rotation and relaxation (µSR) study [22], the corresponding spinon excitations are gapless and form a spinon Fermi surface.…”

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confidence: 82%

“…The lines show NRG theoretical predictions for the Kondo effect of impurities with concentration p = 11(2)% coupled to noninteracting spin-1/2 fermions with the magnetic coupling of a = 31 mT/µB and the Kondo temperature TK = 1.3 K. The low-temperature plateau in K corresponds to a strongly reduced average impurity magnetic moment, M = KB/a = 0.017µB at B = 0.3 T, due to Kondo screening. b, The field dependence of the experimental Knight shift (symbols) deep in the strong-Kondo coupling regime and the NRG theoretical prediction (line).accessible temperatures [20], three orders of magnitude below the dominant exchange interactions [21]. As revealed in our recent muon spin rotation and relaxation (µSR) study [22], the corresponding spinon excitations are gapless and form a spinon Fermi surface.…”

mentioning

confidence: 87%

“…The µSR investigation was conducted on the LTF instrument at the Paul Scherrer Institute (PSI), Switzerland, on a ∼100% deuterated powder sample from the same batch as the one used in our previous investigations [18,21,22]. The sample was glued onto a silver sample holder with diluted GE Varnish to ensure good thermal conductivity.…”

Section: µSr Measurementsmentioning

confidence: 99%

“…Specifically, in Zn-brochantite the temperature dependence of the magnetization (Fig. 2a), the specific heat [2] and the muon-spin-relaxation rate [21] are all smooth and do not feature any kink-like maxima characteristic of spin glasses [25].As the reduction of the impurity magnetization cannot be explained in an impurity-only picture, we next turn to the scenario of impurities coupled to the spinliquid state. Namely, we consider the Kondo effect, where the impurity spin gets screened by spinful itinerant quasiparticles [2].…”

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confidence: 99%

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Kondo screening in a charge-insulating spinon metal

et al. 2019

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The Kondo effect, an eminent manifestation of many-body physics in condensed matter, is traditionally explained as exchange scattering of conduction electrons on a spinful impurity in a metal [1, 2]. The resulting screening of the impurity's local moment by the electron Fermi sea is characterized by a Kondo temperature T K , below which the system enters a non-perturbative strongly-coupled regime. In recent years, this effect has found its realizations beyond the bulkmetal paradigm in many other itinerant-electron systems, such as quantum dots in semiconductor heterostructures [3, 4] and in nanomaterials [5-7], quantum point contacts [8,9], and graphene [10]. Here we report on the first experimental observation of the Kondo screening by chargeless quasiparticles. This occurs in a charge-insulating quantum spin liquid, where spinon excitations forming a Fermi surface take the role of conduction electrons. The observed impurity behaviour therefore bears a strong resemblance to the conventional case in a metal. The discovered spinonbased Kondo effect provides a prominent platform for characterising and possibly manipulating enigmatic host spin liquids.The Kondo screening of a magnetic impurity embedded in a quantum spin liquid (Fig. 1), a highly-quantumentangled yet magnetically disordered state where charge degrees of freedom are frozen, has been the subject of theoretical investigations for more than two decades [11][12][13][14][15][16][17]. In this case, the itinerant electrons of the standard Kondo picture are effectively replaced by emergent fractional magnetic excitations, inherent to any spin liquid. Due to a large variety of essentially different low-energy excitations, spin liquids should be particularly versatile hosts of Kondo physics. In the case of spinon excitations with a Fermi surface -a spinon metal -a Kondolike effect similar to the one in an ordinary metal is expected [13,15]. However, emergent gauge fields mediating spinon-spinon interactions could cause deviations from the generic Fermi-liquid Kondo behaviour. As the spin-liquid Kondo effect has not yet been conclusively confirmed by experiment, these theoretical predictions remain to be verified.Zn-brochantite, ZnCu 3 (OH) 6 SO 4 , is a particularly well-suited compound for investigating the Kondo effect in a spin liquid. This quantum kagome antiferromagnet [2] is one of only a few examples where a spin-liquid state remains stable down to the lowest experimentally 0 1 2 3 0.0 0.5 1.0 1.5 T c weak Kondo coupling spin-polarized impurities T* T K strong Kondo coupling T (K) B (T) gapped spin liquidPhase diagram of Zn-brochantite. Kondo screening of impurity spins (large arrows) by spinons (small arrows) in the spin-liquid state of Zn-brochantite, with the Kondo temperature TK = 1.3 K. The intensity of the blue hue indicates the slope of the imaginary part of the dynamical impurity spin susceptibility χ (ω)/ω at frequency ω → 0. The dotted line marks the contour corresponding to the value at TK and B = 0. The temperature T * denotes the crossover ...

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Magnetic properties of decorated 2D kagome-like lattice

Meng

et al. 2020

Physica A: Statistical Mechanics and its Applications

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Instabilities of spin-liquid states in a quantum kagome antiferromagnet

Cited by 31 publications

References 61 publications

Vanishing Wilson ratio as the hallmark of quantum spin-liquid models

Vanishing Wilson ratio as the hallmark of quantum spin-liquid models

Kondo screening in a charge-insulating spinon metal

Magnetic properties of decorated 2D kagome-like lattice

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