Linear Response in Topological Materials

Noky, Jonathan; Sun, Yan

doi:10.3390/app9224832

Cited by 12 publications

(5 citation statements)

References 132 publications

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“…1a) creates mirror-symmetry-protected Weyl nodal lines in the band structure as encountered by theory and experiments 28,29 . However, the nodal lines lead to vanishing Berry curvature when integrated over the whole Brillouin zone 30,31 and cannot explain the observed phenomena. One way to obtain a large Berry curvature is to gap out their nodal lines using remanent magnetization or an external magnetic field (specifically, to break the mirror symmetry).…”

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confidence: 93%

Spin-polarized Weyl cones and giant anomalous Nernst effect in ferromagnetic Heusler films

et al. 2020

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Weyl semimetals are characterized by the presence of massless band dispersion in momentum space. When a Weyl semimetal meets magnetism, large anomalous transport properties emerge as a consequence of its topological nature. Here, using in−situ spin- and angle-resolved photoelectron spectroscopy combined with ab initio calculations, we visualize the spin-polarized Weyl cone and flat-band surface states of ferromagnetic Co2MnGa films with full remanent magnetization. We demonstrate that the anomalous Hall and Nernst conductivities systematically grow when the magnetization-induced massive Weyl cone at a Lifshitz quantum critical point approaches the Fermi energy, until a high anomalous Nernst thermopower of ~6.2 μVK−1 is realized at room temperature. Given this topological quantum state and full remanent magnetization, Co2MnGa films are promising for realizing high efficiency heat flux and magnetic field sensing devices operable at room temperature and zero-field.

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confidence: 93%

Spin-polarized Weyl cones and giant anomalous Nernst effect in ferromagnetic Heusler films

et al. 2020

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“…Topological materials have attracted tremendous interest in condensed matter physics due to their unique electronic band states, which give rise to novel linear and nonlinear responses [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. Weyl semimetals constitute one class of such topological systems.…”

Section: Introductionmentioning

confidence: 99%

Magnetic and Electronic Properties of Weyl Semimetal Co2MnGa Thin Films

et al. 2021

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Magnetic Weyl semimetals are newly discovered quantum materials with the potential for use in spintronic applications. Of particular interest is the cubic Heusler compound Co2MnGa due to its inherent magnetic and topological properties. This work presents the structural, magnetic and electronic properties of magnetron co-sputtered Co2MnGa thin films, with thicknesses ranging from 10 to 80 nm. Polarized neutron reflectometry confirmed a uniform magnetization through the films. Hard x-ray photoelectron spectroscopy revealed a high degree of spin polarization and localized (itinerant) character of the Mn d (Co d) valence electrons and accompanying magnetic moments. Further, broadband and field orientation-dependent ferromagnetic resonance measurements indicated a relation between the thickness-dependent structural and magnetic properties. The increase of the tensile strain-induced tetragonal distortion in the thinner films was reflected in an increase of the cubic anisotropy term and a decrease of the perpendicular uniaxial term. The lattice distortion led to a reduction of the Gilbert damping parameter and the thickness-dependent film quality affected the inhomogeneous linewidth broadening. These experimental findings will enrich the understanding of the electronic and magnetic properties of magnetic Weyl semimetal thin films.

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“…Last but not least, Heusler compounds offer a notably promising route towards magnetic Weyl semimetals [7]. Weyl semimetals can potentially host unique transport phenomena because of the nontrivial topology of the band structure [8][9][10], which also makes the spin-caloritronic response of Weyl semimentals very interesting [11][12][13][14]. One of the key effects in spin-caloritronic research is the anomalous Nernst effect (ANE), which is the thermal counterpart of the anomalous Hall effect (AHE).…”

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confidence: 99%

Large anomalous Nernst effect in thin films of the Weyl semimetal Co2MnGa

Reichlová

Schlitz

Beckert

et al. 2018

Applied Physics Letters

109

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The magneto-thermoelectric properties of Heusler compound thin films are very diverse. Here, we discuss the anomalous Nernst response of Co 2 MnGa thin films. We systematically study the anomalous Nernst coefficient as a function of temperature, and we show that unlike the anomalous Hall effect, the anomalous Nernst effect in Co 2 MnGa strongly varies with temperature. We exploit the on-chip thermometry technique to quantify the thermal gradient, which enables us to directly evaluate the anomalous Nernst coefficient. We compare these results to a reference CoFeB thin film. We show that the 50-nm-thick Co 2 MnGa films exhibit a large anomalous Nernst effect of -2 µV/K at 300 K, whereas the 10-nm-thick Co 2 MnGa film exhibits a significantly smaller anomalous Nernst coefficient despite having similar volume magnetizations. These findings suggest that the microscopic origin of the anomalous Nernst effect in Co 2 MnGa is complex and may contain contributions from skew-scattering, side-jump or intrinsic Berry phase. In any case, the large anomalous Nernst coefficent of Co 2 MnGa thin films at room temperature makes this material system a very promising candidate for efficient spin-caloritronic devices.

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Linear Response in Topological Materials

Cited by 12 publications

References 132 publications

Spin-polarized Weyl cones and giant anomalous Nernst effect in ferromagnetic Heusler films

Spin-polarized Weyl cones and giant anomalous Nernst effect in ferromagnetic Heusler films

Magnetic and Electronic Properties of Weyl Semimetal Co2MnGa Thin Films

Large anomalous Nernst effect in thin films of the Weyl semimetal Co2MnGa

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