Large intrinsic anomalous Hall effect in half-metallic ferromagnet Co3Sn2S2 with magnetic Weyl fermions

Wang, Qi; Xu, Yuanfeng; Lou, Rui; Liu, Zhonghao; Li, Man; Huang, Yaobo; Shen, Dawei; Weng, Hongming; Wang, Shancai; Lei, Hechang

doi:10.1038/s41467-018-06088-2

Cited by 616 publications

(583 citation statements)

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“…Realization of a Weyl semimetal requires breaking of either inversion (P) or time-reversal (T ) symmetry. Noncentrosymmetric Weyl semimetals that break P but preserve T symmetry have been discovered since 2015 [19,20], but only until more recently have magnetic Weyl semimetals that break T been experimentally discovered [21][22][23][24][25] generated significant interest both for their fundamental physics properties, and for their potential applications such as in spintronics due to their intrinsic magnetism and large observed anomalous Hall conductivity [26,27] as well as in spin caloritronics because of their giant anomalous Nernst coefficient [28].…”

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confidence: 99%

Axion-Field-Enabled Nonreciprocal Thermal Radiation in Weyl Semimetals

et al. 2020

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Objects around us constantly emit and absorb thermal radiation [1][2][3][4][5][6]. The emission and absorption processes are governed by two fundamental radiative properties: emissivity and absorptivity. For reciprocal systems, the emissivity and absorptivity are restricted to be equal by Kirchhoff's law of thermal radiation [1,2,7]. This restriction limits the degree of freedom to control thermal radiation and contributes to an intrinsic loss mechanism in photonic energy harvesting systems such as solar cells [8]. Existing approaches to violate Kirchhoff's law typically utilize conventional magnetooptical effects in the presence of an external magnetic field [9,10]. However, these approaches require either a strong magnetic field (∼3T) [9], or narrow-band resonances under a moderate magnetic field (∼0.3T) [10], because the non-reciprocity in conventional magneto-optical effects is usually weak in the thermal wavelength range. Here, we show that the axion electrodynamics in magnetic Weyl semimetals can be used to construct strongly nonreciprocal thermal emitters that near completely violate Kirchhoffs law over broad angular and frequency ranges, without requiring any external magnetic field. The non-reciprocity moreover is strongly temperature tunable, open new possibilities for active non-reciprocal devices in controlling thermal radiation.[1] G. Kirchhoff, Ueber das Verhältniss zwischen dem Emissionsvermögen und dem Absorptionsvermögen der Körper für Wärme und Licht, Annalen der Physik 185, 275 (1860).

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confidence: 99%

Axion-Field-Enabled Nonreciprocal Thermal Radiation in Weyl Semimetals

et al. 2020

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“…Co3Sn2S2 26,27 ( O~1 .3 × 10 e m/s), Co2MnGa ( O~1 .2 × 10 p m/s) 44 , Y2Ir2O7 (2 × 10 e m/s) [41], and Eu2Ir2O7 (4 × 10 e m/s) 46 . We choose the Weyl node separation 2 = 0.45Å 34 , also close to the separations observed in the above materials.…”

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confidence: 99%

Large nonreciprocal absorption and emission of radiation in type-I Weyl semimetals with time reversal symmetry breaking

et al. 2020

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The equality between the spectral, directional emittance and absorptance of an object under local thermal equilibrium is known as Kirchhoff's law of radiation. The breakdown of Kirchhoff's law of radiation is physically allowed by breaking time-reversal symmetry and can open new opportunities for novel non-reciprocal light emitters and absorbers. Large anomalous Hall conductivity and angle recently observed in topological Weyl semimetals, particularly type-I magnetic Weyl semimetals and type-II Weyl semimetals, are expected to create large nonreciprocal electromagnetic wave propagation. In this work, we focus on type-I magnetic Weyl semimetals and show via modeling and simulation that non-reciprocal surface plasmons polaritons can result in pronounced non-reciprocity without an external magnetic field. The modeling in this work begins with a single pair of Weyl nodes, followed by a more realistic model with multiple paired Weyl nodes. Fermi-arc surface states are also taken into account through the surface conductivity. This work points to the promising applicability of topological Weyl semimetals for magneto-optical and energy applications. . These authors contributed equally to this work. Main textKirchhoff's law of radiation establishes the equality between the spectral, directional absorptance ( , ) and the spectral, directional emittance ( , ) of an object in local thermal equilibrium, i.e., ( , ) = ( , ) , where and are the wavelength and the direction of incoming and outgoing radiation, respectively. Fundamentally, Kirchhoff's law of radiation underlies the theoretical efficiency limit in radiative energy conversion since converting absorbed incoming radiation into another form of energy, such as electricity or heat, always entails the outgoing emission at the same wavelength in the same direction from the object, which causes an intrinsic loss 1-3 . It has been argued 2,4,5 that Kirchhoff's law of radiation is not a required condition for the validity of the second law of thermodynamics in systems that exchange radiative energy, but rather a result of the Lorentz reciprocity theorem in which the only assumptions are a linear constitutive relation and symmetric permittivity and permeability tensors 6,7 . Thus, the violation of Kirchhoff's law of radiation, i.e., non-reciprocity in the spectral, directional absorptance and emittance, is physically allowed, and its realization can open new opportunities for novel light emitters and absorbers for a wide range of radiative applications including solar photovoltaics, thermo-photovoltaics, and antennas 1,8 .Non-reciprocity in a medium often arises due to non-zero anti-symmetric off-diagonal elements of the dielectric tensor of the medium, which creates non-reciprocal electromagnetic modes 9 . One way to create the anti-symmetric off-diagonal elements is by inducing magnetic responses either by the Hall response under an external magnetic field or by spontaneous magnetization in materials, namely the anomalous Hall effect 10 . The anomalous Hall effect can origin...

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“…By stacking, it provides an effective way to realize magnetic WSMs [23,136]. Following that guiding principle, two groups (Liu et al [58] and Wang et al [59]) individually claimed that out-of-plane magnetization The magnetic moments lie inside the xy plane with 2π/3 angles between each two, as shown in Fig. 4(c).…”

Section: Stacking Kagome Latticementioning

confidence: 96%

“…One of the most exotic properties of magnetic WSM is the large intrinsic anomalous Hall effect, Which, in turn, provides a clue for magnetic WSM materials searching. Very recently, several reports proposed the existence of Weyl nodes in layered Kagome lattice [57][58][59]. Inspired by a series of first principles predictions [127][128][129] On the other hand, 2D Kagome lattice with out-of-plane magnetization has become an excellent platform for AHE study [134,135].…”

Section: Stacking Kagome Latticementioning

confidence: 99%

The study of magnetic topological semimetals by first principles calculations

Zou

2019

npj Comput Mater

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Magnetic topological semimetals (TSMs) are topological quantum materials with broken timereversal symmetry (TRS) and isolated nodal points or lines near the Fermi level. Their topological properties would typically reveal from the bulk-edge correspondence principle as nontrivial surface states such as Fermi arcs or drumhead states, etc. Depending on the degeneracies and distribution of the nodes in the crystal momentum space, TSMs are usually classified into Weyl semimetals (WSMs), Dirac semimetals (DSMs), nodal-line semimetals (NLSMs), triple-point semimetals (TPSMs), etc.In this review article, we present the recent advances of magnetic TSMs from a computational perspective. We first review the early predicted magnetic WSMs such as pyrochlore iridates and HgCr2Se4, as well as the recently proposed Heusler, Kagome layers, and honeycomb lattice WSMs.Then we discuss the recent developments of magnetic DSMs, especially CuMnAs in Type-III and EuCd2As2 in Type-IV magnetic space groups (MSGs). Then we introduce some magnetic NLSMs that are robust against spin-orbit coupling (SOC), namely Fe3GeTe2 and LaCl (LaBr). Finally, we discuss the prospects of magnetic TSMs and the interesting directions for future research. *

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Large intrinsic anomalous Hall effect in half-metallic ferromagnet Co3Sn2S2 with magnetic Weyl fermions

Cited by 616 publications

References 46 publications

Axion-Field-Enabled Nonreciprocal Thermal Radiation in Weyl Semimetals

Axion-Field-Enabled Nonreciprocal Thermal Radiation in Weyl Semimetals

Large nonreciprocal absorption and emission of radiation in type-I Weyl semimetals with time reversal symmetry breaking

The study of magnetic topological semimetals by first principles calculations

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