Nonlinear magnetic field dependence of spin polarization in high-density two-dimensional electron systems

The spin polarization ( P ) of high-density InSb two-dimensional electron systems (2DESs) has been measured using both parallel and tilted magnetic fields. P is found to exhibit a superlinear increase with the total field B . This P – B nonlinearity results in a difference in spin susceptibility between its real value χ s and χ gm ∝ m * g * ( m * and g * are the effective mass and g factor, respectively) as routinely used in experiments. We demonstrate that such a P – B nonlinearity originates from the linearly P -dependent g * due to the exchange coupling of electrons rather than from the electron correlation as predicted for the low-density 2DES.