Interband magnetoabsorption study of the shift of the Fermi energy of a 2DEG with an in-plane magnetic field

We investigate experimentally and theoretically the effects of an in-plane magnetic field on the two-dimensional (2D) electron gas via a shift of the Fermi energy in the interband magnetoabsorption. It is shown that the Fermi edge may either shift up (blue) or down (red) in an in-plane magnetic field. The shift depends on the relative strength of two components: (i) the diamagnetic shift of subband edge and (ii) an increase of the 2D density of states which lowers the Fermi energy with respect to the subband edge