Absence of halfmetallicity in defect-free Cr, Mn-delta-doped Digital Magnetic Heterostructures

摘要

We present results of a combined density functional and many-bodycalculations for the electronic and magnetic properties of the defect-freedigital ferromagnetic heterostructures obtained by doping GaAs with Cr and Mn.While local density approximation/(+U) predicts half-metallicity in thesedefect-free delta-doped heterostructures, we demonstrate that local many-bodycorrelations captured by Dynamical Mean Field Theory induce within the minorityspin channel non-quasiparticle states just above $E_F$. As a consequence of theexistence of these many-body states the half-metallic gap is closed and thecarriers spin polarization is significantly reduced. Below the Fermi level theminority spin highest valence states are found to localize more on the GaAslayers being independent of the type of electronic correlations considered.Thus, our results confirm the confinement of carriers in these delta-dopedheterostructures, having a spin-polarization that follow a differenttemperature dependence than magnetization. We suggest that polarizedhot-electron photoluminescence experiments might bring evidence for theexistence of many-body states within the minority spin channel and their finitetemperature behavior.