Ab-initio calculations of spin tunneling through an indirect barrier
1 Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
2 International Centre of Biodynamics, Intrarea Portocalelor Street, Nr.1B, Postal Code 060101, District 6, Bucharest, Romania
3 Arizona State University, Tempe, Arizona, 85284, USA
PMC Physics B 2008, 1:13 doi:10.1186/1754-0429-1-13Published: 6 June 2008
We use a fully relativistic layer Green's functions approach to investigate spin-dependent tunneling through a symmetric indirect band gap barrier like GaAs/AlAs/GaAs heterostructure along  direction. The method is based on Linear Muffin Tin Orbitals and it is within the Density Functional Theory (DFT) in the Local Density Approximation (LDA). We find that the results of our ab-initio calculations are in good agreement with the predictions of our previous empirical tight binding model [Phys. Rev. B, 075313 (2006)]. In addition we show the k||-dependence of the spin polarization which we did not previously include in the model. The ab-initio calculations indicate a strong k||-dependence of the transmission and the spin polarization due to band non-parabolicity. A large window of 25–50% spin polarization was found for a barrier of 8 AlAs monolayers at k|| = 0.03 2π/a. Our calculations show clearly that the appearance of energy windows with significant spin polarization depends mostly on the location of transmission resonances and their corresponding zeros and not on the magnitude of the spin splitting in the barrier.
PACS Codes: 71.70.Ej, 71.15.Mb, 71.55.Eq