Giant suppression of phononic heat transport in a quantum magnet BiCu2PO6

Jeon, Byeong‐Gyun; Koteswararao, B.; Park, C. B.; Shu, G. J.; Riggs, Scott; Moon, Eun-Gook; Chung, Suk Bum; Chou, F. C.; Kim, Kee Hoon

doi:10.1038/srep36970

Cited by 15 publications

(12 citation statements)

References 32 publications

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“…In these cases, phonons and magnetic excitations yield two independent transport channels. On the other hand, a double-peak structure is also known to occur in purely phononic heat transport, resulting from the heat carrying phonons scattering off another degree of freedom, such as a spin excitation with a well defined excitation energy ω 0 [38,39]. Such scattering affects the phononic heat transport over a large temperature range, but has its strongest impact in the temperature regime where the energy of the majority of heat carrying phonons coincides with ω 0 .…”

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confidence: 99%

Unusual Phonon Heat Transport in α−RuCl3 : Strong Spin-Phonon Scattering and Field-Induced Spin Gap

et al. 2018

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The honeycomb Kitaev-Heisenberg model is a source of a quantum spin liquid with Majorana fermions and gauge flux excitations as fractional quasiparticles. Here we unveil the highly unusual low-temperature heat conductivity κ of α-RuCl_{3}, a prime candidate for realizing such physics: beyond a magnetic field of B_{c}≈7.5 T, κ increases by about one order of magnitude, both for in-plane as well as out-of-plane transport. This clarifies the unusual magnetic field dependence unambiguously to be the result of severe scattering of phonons off putative Kitaev-Heisenberg excitations in combination with a drastic field-induced change of the magnetic excitation spectrum. In particular, an unexpected, large energy gap arises, which increases linearly with the magnetic field, reaching remarkable ℏω_{0}/k_{B}≈50 K at 18 T.

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Unusual Phonon Heat Transport in α−RuCl3 : Strong Spin-Phonon Scattering and Field-Induced Spin Gap

et al. 2018

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“…Conventional phonon thermal conductivity in a magnetic insulator is ascribed to four contributions, point defects, grain boundaries, Umklapp processes, and magnonphonon resonant scattering [37][38][39]. The last has been used successfully to describe the H-dependence of features observed in κ in several low-dimensional materials [10,40,41]. However, its effect is usually to generate a minimum at the resonance energy, causing a double-peak structure in κ(T ) where only the lower peak has strong H-dependence [8,10,41].…”

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Anomalous Thermal Conductivity and Magnetic Torque Response in the Honeycomb Magnet α−RuCl3

et al. 2017

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We report on the unusual behavior of the in-plane thermal conductivity κ and torque τ response in the Kitaev-Heisenberg material α-RuCl_{3}. κ shows a striking enhancement with linear growth beyond H=7 T, where magnetic order disappears, while τ for both of the in-plane symmetry directions shows an anomaly at the same field. The temperature and field dependence of κ are far more complex than conventional phonon and magnon contributions, and require us to invoke the presence of unconventional spin excitations whose properties are characteristic of a field-induced spin-liquid phase related to the enigmatic physics of the Kitaev model in an applied magnetic field.

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“…Intriguing heat conductivity results for one-dimensional spin systems with relatively small exchange interactions have been obtained for both organic and inorganic materials, see e.g. [32,[172][173][174][175] for S = 1/2 systems and [28,30,55,[176][177][178][179] for systems with large spin, see also the reviews [180,181].…”

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confidence: 95%

Heat transport of cuprate-based low-dimensional quantum magnets with strong exchange coupling

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2019

Physics Reports

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Transport properties provide important access to a solid's quasiparticles, such as quasiparticle density, mobility, and scattering. The transport of heat can be particularly revealing because, in principle, all types of excitations in a solid may contribute. Heat transport is well understood for phonons and electrons, but relatively little is known about heat transported by magnetic excitations. However, during the last about two decades, the magnetic heat transport attracted increasing attention after the discovery of large and unusual signatures of it in low-dimensional quantum magnetic cuprate materials. Today it constitutes an important probe to otherwise often elusive, topological quasiparticles in a broader class of quantum magnets. This review summarizes the experimental foundation of this research, i.e. the state of the art for the magnetic heat transport in the mentioned cuprate materials which host prototypical low-dimensional antiferromagnetic S = 1/2 Heisenberg models. These comprise, in particular, the two-dimensional square lattice, and one-dimensional spin chain and two-leg ladder spin models. It is shown, how studying the heat transport provides direct access to the thermal occupation and the scattering of the already quite exotic quasiparticles of these models which range from spin-1 spin wave and triplon excitations to fractionalized spin-1/2 spinons. Remarkable transport properties of these quasiparticles have been revealed: the spin-heat transport often is highly efficient and in some cases even ballistic, in agreement with theoretical predictions. We are considering S = 1/2 models with Heisenberg interactionwhere the sum runs over all nearest neighbors in the system. Here we are investigating three different spin models: the 2D-HAF, the two-leg spin ladder, and spin chains. For the 2D-HAF and the spin chain J i,j = J and for the spin ladder J i,j = J along the legs and J i,j = J ⊥ along the rungs of the ladder. The corresponding low-dimensional quantum spin models are characterized by very peculiar ground states which are quantum disordered in the one-dimensional chain and ladder models. The elementary excitations which emerge from this ground states bear therefore a quite exotic character. For instance, the spin-spin correlations of S = 1/2 Heisenberg spin chains, decay algebraically with distance between the spins [65]. The elementary excitations are nevertheless well defined. They are fractionalized, i.e. ∆S = 1 spin-flip excitations of the system decay into so-called spinons which are gapless and carry a spin S = 1/2 [66]. On the other hand, the ground state of a two-leg ladder possesses more short-range spin-spin correlations which decay exponentially as a function of distance [67,68]. The elementary excitations are S = 1 particles (usually called magnons or triplons) and are separated from the ground state by a spin gap ∆ (∆/k B ≈ 400 K in the case of the systems discussed here) [68]. Finally, the ground state of the 2D-HAF is a rather classical longrange ordered Néel state. However, al...

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Giant suppression of phononic heat transport in a quantum magnet BiCu2PO6

Cited by 15 publications

References 32 publications

Unusual Phonon Heat Transport in α−RuCl3 : Strong Spin-Phonon Scattering and Field-Induced Spin Gap

Unusual Phonon Heat Transport in α−RuCl3 : Strong Spin-Phonon Scattering and Field-Induced Spin Gap

Anomalous Thermal Conductivity and Magnetic Torque Response in the Honeycomb Magnet α−RuCl3

Heat transport of cuprate-based low-dimensional quantum magnets with strong exchange coupling

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