The average electron spin polarization P of a two-dimensional electron gas confined in GaAs/GaAlAs multiple quantum wells was measured by NMR near the fractional quantum Hall state with filling factor ν = 2/3. Above this filling factor (2/3 ≤ ν < 0.85), a strong depolarization is observed corresponding to two spin flips per additional flux quantum. The most remarkable behavior of the polarization is observed at ν = 2/3, where a quantum phase transition from a partially polarized (P ≈ 3/4) to a fully polarized (P = 1) state can be driven by increasing the ratio between the Zeeman and the Coulomb energy above a critical value ηC = ΔZ/ΔC = 0.0185.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)