Small-Angle Shubnikov–de Haas Measurements in a 2D Electron System: The Effect of a Strong In-Plane Magnetic Field

Measurements in magnetic fields applied at small angles relative to the electron plane in silicon MOSFETs indicate a factor of 2 increase of the frequency of Shubnikov–de Haas oscillations at $H>\mathrm{}{H}_{\mathrm{sat}}$. This signals the onset of full spin polarization above $H_{\mathrm{sat}}$, the parallel field above which the resistivity saturates to a constant value. For $H<\mathrm{}{H}_{\mathrm{sat}}$, the phase of the second harmonic of the oscillations relative to the first is consistent with scattering events that depend on the overlap instead of the sum of the spin-up and spin-down densities of states. This unusual behavior may reflect the importance of many-body interactions.