Kavli Affiliate: Leon Balents
| First 5 Authors: Nisarga Paul, Takamori Park, Jung Hoon Han, Leon Balents,
| Summary:
We study the gyrotropic magnetic effect (GME), the low-frequency limit of
optical gyrotropy, in metals and semimetals coupled to chiral spin textures. In
these systems, the chiral spin texture which lacks inversion symmetry can
imprint itself upon the electronic structure through Hund’s coupling, leading
to novel low-frequency optical activity. Using perturbation theory and
numerical diagonalization of both relativistic and non-relativistic models of
conduction electrons coupled to spin textures, we analyze how the GME manifests
in both single-$q$ and multi-$q$ textures. Analytical expressions for the
rotatory power are derived in terms of universal scaling functions. Estimates
based on realistic material parameters reveal an experimentally viable range of
values for the rotatory power. The GME arises from the orbital and spin
magnetic moments of conduction electrons, with the orbital part closely tied to
Berry curvature and playing a significant role in relativistic metals but not
so in non-relativistic metals where there is no inherent Berry curvature. The
spin contribution to the GME can be significant in non-relativistic metals with
a large Fermi energy. Our work establishes the GME as a sensitive probe of
magnetic chirality and symmetry breaking in metallic chiral magnets.
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