Spin splitting of two-dimensional states in the conduction band of asymmetric heterostructures: Contribution from the atomically sharp interface

The effect of an atomically sharp impenetrable interface on the spin splitting of the spectrum of two-dimensional electrons in heterostructures based on (001) III-V has been analyzed. To this end, the single-band Hamiltonian I"(6) for envelope functions is supplemented by a general boundary condition taking into account the possibility of the existence of Tamm states. This boundary condition also takes into account the spin-orbit interaction, the asymmetry of a quantum well, and the noncentrosymmetricity of the crystal and contains the single phenomenological length R characterizing the structure of the interface at atomic scales. The model of a quasi-triangular well created by the field F has been considered. After the unitary transformation to zero boundary conditions, the modified Hamiltonian contains an interface contribution from which the two-dimensional spin Hamiltonian is obtained through averaging over the fast motion along the normal. In the absence of magnetic field B, this contribution is the sum of the Dresselhaus and Bychkov-Rashba terms with the constants renormalized owing to the interface contribution. In the field B containing the quantizing component B (z) , the off-diagonal (in cubic axes) components of the g factor tensor are linear functions of |B (z) | and the number of the Landau level N. The results are in qualitative agreement with the experimental data.