Electron spin resonance and nuclear spin pumping in 2DEG quantum Hall system

We prepare a microwave electron spin resource (ESR) cavity for detecting a response from a 2DEG in an n-AlGaAs/GaAs. The response is obtained as a change in the longitudinal resistance (Δρxx) in ν=3 quantum Hall region, particularly as a peak in Δρxx for resonance. We use the data of ESR to evaluate the g-factor and the lower bound for dephasing time. The resonance magnetic field suffers from nuclear spin effects via the hyperfine coupling, resulting in the ESR peak shift. We find the ESR peak shift or Overhauser shift decays with two time constants, suggesting the existence of two different origins for the relaxation.