Evidence for Ballistic Thermal Conduction in the One-DimensionalS=1/2 Heisenberg Antiferromagnetic Spin System Sr2CuO3

Takahashi, Nobuo; Adachi, Tadashi; Noji, Takashi; Kudo, Kazuhiro; Kobayashi, Norio; Koike, Yasuhiro

doi:10.1143/jpsj.77.034607

Cited by 41 publications

(89 citation statements)

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“…spinon-defect Thus we have l −1 mag = l −1 0 + l −1 sp , where l 0 describes the T -independent spinon-defect scattering whereas l sp (T ) accounts for the T -dependent spinon-phonon scattering. For the latter, we assume a general umklapp process with a characteristic energy scale k B T * u of the order of the relevant phonon energies, which is commonly used in literature [1,2,4,6,35]. Thus we get the expression,…”

Section: Resultsmentioning

confidence: 99%

“…Experimental investigations on these compounds by doping impurities in a controlled fashion have shown that a quantitatively reasonable description of the temperature dependence of spinon mean free paths is possible by taking into account the scattering of magnetic excitations off phonons and impurities alone [1,2,5,6,17].…”

Section: Introductionmentioning

confidence: 99%

“…The materials' heat transport parallel to the chains is known to consist of a large contribution from spinons in addition to conventional phononic transport [1,2,[4][5][6]. Earlier, SrCuO 2 has been studied with regard to the effect of substituting Ca for Sr in small amounts [3,32].…”

Section: Introductionmentioning

confidence: 99%

“…We observe a gradual but significant suppression of the spinon heat conductivity (κ mag ) with increasing amount of Ca content which extends up to the highest doping level of 50 %, and thus is fundamentally different from that observed for the double chain compound SrCuO 2 . Thus, Ca, an off-chain impurity, results in a more subtle effect than in-chain impurities [6] thereby making it possible to probe a large doping regime up to very high doping levels.…”

Section: Introductionmentioning

confidence: 99%

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Bond disorder and spinon heat transport in theS=12Heisenberg spin chain compound Sr2CuO3: From

et al. 2014

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We investigate the effect of disorder on the heat transport properties of the S = 1 2 Heisenberg chain compound Sr2CuO3 upon chemically substituting Sr by increasing concentrations of Ca. As Ca occupies sites outside but near the Cu-O-Cu spin chains, bond disorder, i.e. a spatial variation of the exchange interaction J, is expected to be realized in these chains. We observe that the magnetic heat conductivity (κmag) due to spinons propagating in the chains is gradually but strongly suppressed with increasing amount of Ca, where the doping dependence can be understood in terms of increased scattering of spinons due to Ca-induced disorder. This is also reflected in the spinon mean free path which can be separated in a doping independent but temperature dependent scattering length due to spinon-phonon scattering, and a temperature independent but doping dependent spinon-defect scattering length. The latter spans from very large (> 1300 lattice spacings) to very short (∼ 12 lattice spacings) and scales with the average distance between two neighboring Ca atoms. Thus, the Ca-induced disorder acts as an effective defect within the spin chain, and the doping scheme allows to cover the whole doping regime between the clean and the dirty limits. Interestingly, at maximum impurity level we observe, in Ca-doped Sr2CuO3, an almost linear increase of κmag at temperatures above 100 K which reflects the intrinsic low temperature behavior of heat transport in a Heisenberg spin chain. These findings are quite different from that observed for the Ca-doped double spin chain compound, SrCuO2, where the effect of Ca seems to saturate already at intermediate doping levels.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bond disorder and spinon heat transport in theS=12Heisenberg spin chain compound Sr2CuO3: From

et al. 2014

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“…3e) might be attributed to an inevitable slight misalignment of ∇T direction from the b-axis (≤ 6 • ). We also note that the thermal conductivity of Sr 2 CuO 3 is almost isotropic [22] and, therefore, the voltage suppression cannot be attributed to a reduction in the magnitude of ∇T . The negative and anisotropic LSSE is evidence that spin current is generated and conveyed by spinons through the spin chains of the Sr 2 CuO 3 .…”

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confidence: 80%

One-dimensional spinon spin currents

et al. 2016

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1Spin liquid is a state of electron spins where quantum fluctuation breaks magnetic ordering with keeping spin correlation [1]. It has been one of central topics of magnetism because of its relevance to fascinating phenomena such as high-T c superconductivity [2, 3] and topological states [4]. In spite of the profound physics, on the other hand, spin liquid itself has been quite difficult to utilize.Typical spin liquid states are realized in one-dimensional spin systems, called quantum spin chains [5, 6]. Here we show that a spin liquid in a spin-1/2 quantum chain generates and carries spin current via its long-range spin fluctuation. This is demonstrated by observing an anisotropic negative spin Seebeck effect [7][8][9][10][11][12] along the spin chains in Sr 2 CuO 3 . The result shows that spin current can flow even in an atomic channel owing to the spin liquid state, which can be used for atomic spin-current wiring.A flow of electrons spin angular momentum is called spin current [13]. In condensed matter science, transport properties of spin current have attracted considerable interest since the discovery of various spin-current phenomena [14, 15]. In spintronics [16], on the other hand, it is of critical importance to find materials which can carry spin angular momentum efficiently in integrated microscopic devices.Two types of spin current have experimentally been explored so far. The first one is conduction-electron spin current, which is mediated by an electron motion in metals and semiconductors. Its velocity and propagation length are thus limited by electron diffusion [17]. The other type is spin-wave spin current [18,19], where spin waves, wavelike propagation of spin motions in magnets, carry spin angular momentum. Its excitation gap is equal to a spin-wave gap, proportional to magnetic anisotropy. Importantly, spin-wave spin current can exist even in insulators in which spin relaxation via conduction electrons is absent, an advantage which may realize fast and long-range spin current transmission, opening a new field of insulator-based spintronics. However, spin-wave spin current in classical magnets may not be suitable for microscopic devices, since handling spin waves becomes difficult when devices are miniaturized toward atomic scale; in ferromagnets, spontaneous magnetization brings about significant stray fields, causing crosstalk. In an antiferromagnetic system, on the other hand, spin ordering patterns should be broken or interfered when a device is in atomic scale; in both cases, spin waves become vulnerable. Therefore, to realize spin-current transport in microscopic devices, spin ordering is expected to vanish with 2 keeping strong interaction among spins.Here, we would like to make a new type of spin current debut: spinon spin current, which may provide a channel for atomic spin transmission to satisfy the requirements. A spinon generally refers to magnetic elementary excitation in quantum spin liquid states [1]. When system size of a magnet is reduced to atomic scale, quantum spin fluct...

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

Heß

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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Evidence for Ballistic Thermal Conduction in the One-DimensionalS=1/2 Heisenberg Antiferromagnetic Spin System Sr₂CuO₃

Abstract: We have measured the thermal conductivity of the one-dimensional (1D) S = 1/2 Heisenberg antiferromagnetic spin system of Sr

Cited by 41 publications

References 34 publications

Bond disorder and spinon heat transport in theS=12Heisenberg spin chain compound Sr2CuO3: From

Bond disorder and spinon heat transport in theS=12Heisenberg spin chain compound Sr2CuO3: From

One-dimensional spinon spin currents

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

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