We theoretically study the thermal Hall effect by magnons in skyrmion crystal phases of ferrimagnets in the vicinity of the angular momentum compensation point (CP). To this end, we start by deriving the equation of motion for magnons in the background of an arbitrary equilibrium spin texture, which gives rise to the fictitious electromagnetic field for magnons. As the net spin density varies, the resultant equation of motion interpolates between the relativistic Klein-Gordon equation at the CP and the nonrelativistic Schrödinger-like equation away from it. In skyrmion crystal phases, the right- and the left-circularly polarized magnons, with respect to the order parameter, are shown to form the Landau levels separately within the uniform skyrmion-density approximation. For an experimental proposal, we predict that the magnonic thermal Hall conductivity changes its sign when the ferrimagnet is tuned across the CP, providing a way to control heat flux in spin-caloritronic devices on the one hand and a feasible way to detect the CP of ferrimagnets on the other hand.
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http://dx.doi.org/10.1103/PhysRevLett.122.057204 | DOI Listing |
Angew Chem Int Ed Engl
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Leibniz-Institut fur Festkorper- und Werkstoffforschung Dresden eV, Helmholtzstraße 20, 01069, Dresden, GERMANY.
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Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91011, USA.
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View Article and Find Full Text PDFMater Horiz
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Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York 14853, USA.
As the demand for high-power-density microelectronics rises, overheating becomes the bottleneck that limits device performance. In particular, the heterogeneous integration architecture can magnify the importance of heat dissipation and necessitate electrical insulation between critical junctions to prevent dielectric breakdown. Consequently, there is an urgent need for thermal interface materials (TIMs) with high thermal conductivity and electrical insulation to address this challenge.
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College of Sciences, Northeastern University, Shenyang, 110819, China.
In this work, using first-principles calculations, we predict a promising class of two-dimensional ferromagnetic semiconductors, namely Janus PrXY (X ≠ Y = Cl, Br, I) monolayers. Through first-principles calculations, we found that PrXY monolayers have excellent dynamic and thermal stability, and their band structures, influenced by magnetic exchange and spin-orbital coupling, exhibit significant valley polarization. Between and - valleys, the Berry curvature values are opposite to each other, resulting in the anomalous valley Hall effect.
View Article and Find Full Text PDFAdv Mater
January 2025
Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK.
Thick metamorphic buffers are considered indispensable for III-V semiconductor heteroepitaxy on large lattice and thermal-expansion mismatched silicon substrates. However, III-nitride buffers in conventional GaN-on-Si high electron mobility transistors (HEMT) impose a substantial thermal resistance, deteriorating device efficiency and lifetime by throttling heat extraction. To circumvent this, a systematic methodology for the direct growth of GaN after the AlN nucleation layer on six-inch silicon substrates is demonstrated using metal-organic vapor phase epitaxy (MOVPE).
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