Weak spin-orbit interactions induce exponentially flat mini-bands in magnetic metals without inversion symmetry

I. Fischer; A. Rosch

doi:doi:10.1209/epl/i2004-10174-9

Europhys. Lett., 68 (1), pp. 93-99 (2004)
DOI: 10.1209/epl/i2004-10174-9

Weak spin-orbit interactions induce exponentially flat mini-bands in magnetic metals without inversion symmetry

I. Fischer and A. Rosch

Institut für Theoretische Physik, Universität zu Köln - 50937 Köln, Germany

received 10 June 2004; accepted 5 August 2004

Abstract
In metallic magnets like $\chem{MnSi}$ the interplay of two very weak spin-orbit coupling effects can strongly modify the Fermi surface. In the absence of inversion symmetry even a very small Dzyaloshinsky-Moriya interaction of strength $\delta\ll 1$ distorts a ferromagnetic state into a chiral helix with a long pitch of order $1/\delta$ . We show that additional small spin-orbit coupling terms of order $\delta$ in the band structure lead to the formation of exponentially flat mini-bands with a bandwidth of order $e^{-1/\sqrt{\delta}}$ parallel to the direction of the helix. These flat mini-bands cover a rather broad belt of width $\sqrt{\delta}$ on the Fermi surface where electron motion parallel to the helix practically stops. We argue that these peculiar band structure effects lead to pronounced features in the anomalous skin effect.

PACS
75.30.-m - Intrinsic properties of magnetically ordered materials.
75.47.-m - Magnetotransport phenomena; materials for magnetotransport.
71.20.-b - Electron density of states and band structure of crystalline solids.

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