Local investigation of the energy gap within the incompressible strip in the quantum Hall regime

We experimentally study the energy gap within the incompressible strip at local filling factor $\nu_c=1$ at the quantum Hall edge for samples of very different mobilities. The obtained results indicate strong enhancement of the energy gap in comparison to the single-particle Zeeman splitting. We identify the measured gap as a mobility gap, so a pronounced experimental in-plane magnetic field dependence can both be attributed to the spin effects as well as to the change in the energy levels broadening.