NMR probing of spin and charge order near odd-integer filling in the second Landau level

摘要

Studies of spin degrees of freedom near odd-integer filling v = 3 in the second Landau level have engendered conflicting accounts of the spin properties in this regime. Using resistively detected NMR as a probe of local spin density, we explore the nature of the ground state in the quantum Hall regime near v = 3. Our Knight shift measurements reveal anomalies in NMR spectral line shapes near v = 3, which demonstrate the presence of solid phases formed from charged quasiparticles, with maximal spin polarization (i.e., no additional spin flips) at each v. The long nuclear spin relaxation times demonstrate the absence of Skyrmions, or spin textures, in this phase. On the basis of these observations, we attempt to reconcile conflicting reports on the quasiparticle properties and spin wave excitations at v ～ 3, which may engender new paradigms for the understanding of spin excitations in a collinear ferromagnet with broken translational symmetry.