Europhys. Lett.
Volume 68, Number 1, October 2004
Page(s) 93 - 99
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 September 2004
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

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.

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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