Abstract
Quantum states characterized by nontrivial topology produce interesting electrodynamics and versatile electronic functionalities. One source for such remarkable phenomena is emergent electromagnetic field, which is the outcome of interplay between topological spin structures with scalar spin chirality and conduction electrons. However, it has scarcely been exploited for emergent function related to heat-electricity conversion. Here we report an unusually enhanced thermopower by application of magnetic field in MnGe hosting topological spin textures. By considering all conceivable origins through quantitative investigations of electronic structures and properties, a possible origin of large magneto-thermopower is assigned to the strong energy dependence of charge-transport lifetime caused by unconventional carrier scattering via the dynamics of emergent magnetic field. Furthermore, high-magnetic-field measurements corroborate the presence of residual magnetic fluctuations even in the nominally ferromagnetic region, leading to a subsisting behavior of field-enhanced thermopower. The present finding may pave a way for thermoelectric function of topological magnets.
Highlights
Quantum states characterized by nontrivial topology produce interesting electrodynamics and versatile electronic functionalities
Its increment ratio becomes prominent at low temperatures: S shows a typical value for ordinary metals at zero field (e.g., −5.5 μV K−1 at 15 K), and it develops an order of magnitude larger at 14 T (e.g., 26 μV K−1 at 15 K)
Phase transition from hedgehog lattice (HL, Fig. 1a) to ferromagnetic (FM) state at the critical magnetic field Hc is recognized as a kink in the S–H curve, followed by a saturating behavior
Summary
Quantum states characterized by nontrivial topology produce interesting electrodynamics and versatile electronic functionalities One source for such remarkable phenomena is emergent electromagnetic field, which is the outcome of interplay between topological spin structures with scalar spin chirality and conduction electrons. It has scarcely been exploited for emergent function related to heat-electricity conversion. It commonly occurs in metals that entropy flows of electrons with their potential energy above and below εF S on the order of a cancel out with each few μV K−1 This is other, resulting in small because the Fermi distribution function permits only electrons within their energy range approximately between εF ± kBT to be involved in heat transport phenomena, and electrons above and below εF carry heat (product of entropy and temperature) with opposite signs. The Mott formula suggests that such cancellation can be avoided in the presence of difference in number, velocity, and scattering arbaryete∂mbln∂eeτεtaðwεsÞue εre1⁄4endεFe.bleyIcnttrdhoeenedsd,earbaiovsyvamteivamened∂tlrnbi∂DceεðloεbÞw aεn1⁄4εdεFF, the first two of which and the last of which structures around εF generate large S (e.g., pseudogap structures in Heusler compounds3), whereas Kondo scattering creates strong energy dependence in τ and the consequent exotic Seebeck effect in rareearth compounds[4]
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