Volume 90, Number 4, May 2010
|Number of page(s)||5|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||04 June 2010|
Spin helix of magnetic impurities in two-dimensional helical metal
College of Material Science and Optoelectronics Technology, Graduated University of Chinese Academy of Science Beijing 100049, China
2 Institute for Advanced Study, Tsinghua University - Beijing 100084, China
3 Department of Physics, Shanghai Jiaotong University - Shanghai 200240, China
4 Institute of Theoretical Physics, Chinese Academy of Science - Beijing 100089, China
Corresponding author: email@example.com
Accepted: 4 May 2010
The surface state of a topological insulator dubbed as helical metal is a unique metallic system, which exhibits one single Dirac cone and spin-momentum locking. We show that the behaviors of magnetic impurities embedded in this kind of surface states manifest the uniqueness of helical metals among other conventional Dirac materials such as graphene. We find there is a significant Dzyaloshinskii-Moriya (DM) term among the effective interactions between impurity spins mediated by the conduction electrons. For a chain of impurity spins, we show that such a DM interaction gives rise to a single-handed spin helix state, the handedness of which is locked with the sign of the Fermi velocity of the emergent Dirac fermions. We also point out that the polarization of impurity spins can be controlled via electric voltage for dilute magnetic-impurity concentration.
PACS: 75.30.Hx – Magnetic impurity interactions / 73.20.-r – Electron states at surfaces and interfaces / 72.25.Dc – Spin polarized transport in semiconductors
© EPLA, 2010
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