"Fingerprint of different spin–orbit terms for spin transport in HgTe quantum wells "

D G Rothe: R W Reinthaler, C-X Liu, L W Molenkamp, S-C Zhang and E M Hankiewicz; New J. Phys., 06/17/10.

Additional Authors: R W Reinthaler, C-X Liu, L W Molenkamp, S-C Zhang and E M Hankiewicz

Abstract:

Using kcenterdotp theory, we derive an effective four-band model describing the physics of the typical two-dimensional topological insulator (HgTe/CdTe quantum well (QW)) in the presence of an out-of-plane (in the z-direction) inversion breaking potential and an in-plane potential. We find that up to third order in perturbation theory, only the inversion breaking potential generates new elements to the four-band Hamiltonian that are off-diagonal in spin space. When this new effective Hamiltonian is folded into an effective two-band model for the conduction (electron) or valence (heavy hole) bands, two competing terms appear: (i) a Rashba spin–orbit interaction originating from inversion breaking potential in the z-direction and (ii) an in-plane Pauli term as a consequence of the in-plane potential. Spin transport in the conduction band is further analysed within the Landauer–Büttiker formalism. We find that for asymmetrically doped HgTe QWs, the behaviour of the spin-Hall conductance is dominated by the Rashba term.