title: New phase transition between partially and fully polarized quantum Hall states with charge and spin gaps at nu = 2/3.
abstract: The average electron spin polarization Rho 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 nu = 2/3. Above this filling factor (2/3< or = nu < 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 nu = 2/3, where a quantum phase transition from a partially polarized (Rho approximately 3/4) to a fully polarized (Rho = 1) state can be driven by increasing the ratio between the Zeeman and the Coulomb energy above a critical value eta(c) = Delta(Z)/Delta(C) = 0.0185.
authors.affiliation: Grenoble High Magnetic Field Laboratory, MPI-FKF and CNRS, BP 166, F-38042 Grenoble Cedex 9, France. freytag@polycnrs-gre.fr
authors.forename: N
authors.initials: N
authors.lastname: Freytag
authors.forename: Y
authors.initials: Y
authors.lastname: Tokunaga
authors.forename: M
authors.initials: M
authors.lastname: Horvatić
authors.forename: C
authors.initials: C
authors.lastname: Berthier
authors.forename: M
authors.initials: M
authors.lastname: Shayegan
authors.forename: L P
authors.initials: LP
authors.lastname: Lévy