We present a study of electric, thermal and thermoelectric response in noncollinear antiferromagnet Mn3Sn, which hosts a large Anomalous Hall Effect (AHE). Berry curvature generates off-diagonal thermal(Righi-Leduc) and thermoelectric(Nernst) signals, which are detectable at room temperature and invertible with a small magnetic field. The thermal and electrical Hall conductivities respect the Wiedemann-Franz law, implying that the transverse currents induced by Berry curvature are carried by Fermi surface quasi-particles. In contrast to conventional ferromagnets, the anomalous Lorenz number remains close to the Sommerfeld number over the whole temperature range of study, excluding any contribution by inelastic scattering and pointing to Berry curvature as the unique source of AHE. The anomalous off-diagonal thermo-electric and Hall conductivities are strongly temperature-dependent and their ratio is close to kB/e.The ordinary Hall effect, the transverse electric field generated by a longitudinal charge current in presence of a magnetic field, is caused by the Lorentz force exerted by magnetic field on charge carriers. In ferromagnetic solids, there is an additional component to this response (known as extraordinary or anomalous), thought to arise as a result of a sizeable magnetization. During the past decade, a clear link between the Anomalous Hall Effect (AHE) and the Berry curvature of Bloch waves has been established [1,2]. Charged carriers of entropy are also affected by the Lorenz force. Therefore, one expects a transverse component to thermal conductivity called the Righi-Leduc (or the thermal Hall) effect [3] in presence of magnetic field. This is also the case of thermoelectric conductance, which acquires an off-diagonal component, α ij , intimately linked to the Nernst coefficient, directly measurable by experiment [4]. When the Berry curvature replaces the magnetic field, counterparts of the AHE appear in the thermal and thermoelectric response of ferromagnets [5][6][7][8]. They can be an additional source of information regarding the fundamental mechanism leading to the generation of dissipationless transverse currents. Recently, following a proposition by Chen, Niu and Macdonald[9], Nakasutji et al. and Nayak et al. found a large AHE in Mn 3 Sn [10] and Mn 3 Ge [11,12], which are noncollinear antiferromagnets at room temperature. Several recent theoretical studies were devoted to this issue [13][14][15].In this letter, we present a study of Anomalous Righi-Leduc and Nernst effects (ANE) in Mn 3 Sn in order to quantify the amplitude of these coefficients compared to their Hall counterpart.We detect a large Anomalous Righi-Leduc conductivity and find that its magnitude corresponds to what is expected according to the Wiedemann-Franz (WF) Law over an extended temperature window. The result confirms a theoretical prediction by Haldane[16] with important consequences for the debate regarding the two alternative formulations of anomalous Hall effect [16][17][18]. AHE can be formulated as a property of th...

Intrinsic anomalous Nernst effect (ANE), like its Hall counterpart, is generated by Berry curvature of electrons in solids. Little is known about its response to disorder. In contrast, the link between the amplitude of the ordinary Nernst coefficient (ONE) and the mean-free-path is extensively documented. Here, by studying Co3Sn2S2, a topological half-metallic semimetal hosting sizable and recognizable ordinary and anomalous Nernst responses, we demonstrate an anti-correlation between the amplitude of ANE and carrier mobility. We argue that the observation, paradoxically, establishes the intrinsic origin of the ANE in this system. We conclude that various intrinsic off-diagonal coefficients are set by the way the Berry curvature is averaged on a grid involving the mean-free-path, the Fermi wavelength and the de Broglie thermal length.

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Magnetic Weyl semimetals (WSMs) bearing long-time pursuing are still very rare. We herein identified magnetic exchange induced Weyl state in EuCd 2 Sb 2 , a semimetal in type IV magnetic space group, via performing high magnetic field

Co3Sn2S2 is a ferromagnetic semi-metal with Weyl nodes in its band structure and a large anomalous Hall effect below its Curie temperature of 177 K. We present a detailed study of its Fermi surface and examine the relevance of the anomalous transverse Wiedemann Franz law to it. We studied Shubnikov-de Haas oscillations along two orientations in single crystals with a mobility as high as cm2 V−1 s−1 subject to a magnetic field as large as ∼60 T. The angle dependence of the frequencies is comparable with density functional theory (DFT) calculations and reveals two types of hole pockets (H1, H2) and two types of electron pockets (E1, E2). An additional unexpected frequency emerges at high magnetic field. We attribute it to magnetic breakdown between the hole pocket H2 and the electron pocket E2, since it is close to the sum of the E2 and H2 fundamental frequencies. By measuring the anomalous thermal and electrical Hall conductivities, we quantified the anomalous transverse Lorenz ratio, which is close to the Sommerfeld ratio () below 100 K and deviates downwards at higher temperatures. This finite temperature deviation from the anomalous Wiedemann–Franz law is a source of information on the distance between the sources and sinks of the Berry curvature and the chemical potential.