Anisotropic nuclear spin relaxation and dynamic polarization rates in the ν = 2/3 quantum Hall states

Abstract

We present an anisotropy of the hysteretic transport due to the dynamic nuclear polarization (DNP) around the spin transition point at Landau level filling factor ν = 2/3 in tilted magnetic field. When the direction of the in-plane component of the magnetic field B|| is normal to the probe current J, a strong hysteresis related with DNP occurs. On the other hand, as B|| is parallel to I, the hysteresis almost disappears. To clear the origin of the anisotropy of DNP, we study the nuclear spin-lattice relaxation and nuclear spin polarization rates at the transition point and find out that they are anisotropic for a relative angle between B|| and I.