Enhancement of the ν=5/2 Fractional Quantum Hall State in a Small In-Plane Magnetic Field

Using a 50-nm-width ultraclean GaAs/AlGaAs quantum well, we have studied the Landau level filling factor nu = 5/2 fractional quantum Hall effect in a perpendicular magnetic field B similar to 1.7 T and determined its dependence on tilted magnetic fields. Contrary to all previous results, the 5/2 resistance minimum and the Hall plateau are found to strengthen continuously under an increasing tilt angle 0 < theta < 25 degrees (corresponding to an in-plane magnetic field 0 < B-parallel to < 0.8 T). In the same range of theta, the activation gaps of both the 7/3 and the 8/3 states are found to increase with tilt. The 5/2 state transforms into a compressible Fermi liquid upon tilt angle theta > 60 degrees, and the composite fermion series [2 + p/(2p +/- 1), p = 1, 2] can be identified. Based on our results, we discuss the relevance of a Skyrmion spin texture at nu = 5/2 associated with small Zeeman energy in wide quantum wells, as proposed by Wojs et al. [Phys. Rev. Lett. 104, 086801 (2010)].