Electron spin resonance of the two-dimensional metallic state and the quantum Hall state in a Si/SiGe quantum well

We report electrically detected electron spin resonance (ESR) measurements of a high mobility two-dimensional (2D) electron system formed in a Si/SiGe quantum well, with millimeter wave (100GHz) in a high magnetic field (3.55T). The negative ESR signal observed under an in-plane magnetic field gives direct evidence that the spin polarization leads to a resistance increase in the 2D metallic state. Suppression of spin decoherence was observed in the quantum Hall state at the Landau level filling factor ν=2ν=2. Strength of the nuclear magnetic field in the resonance is evaluated to be less than 0.1mT, much smaller than that reported for GaAs/AlGaAs heterostructures.