Observation of a Fractional Quantum Hall State at $\nu=1/4$ in a Single Wide GaAs Quantum Well

We have preformed low temperature ($T\sim35$ mK) transport measurements using a 50 nm high-quality GaAs quantum well with an electron density of $n_e=2.55\times10^{11}$ cm$^{-2}$ and a mobility of $\mu \sim 10^{7}$ cm$^2$/Vs. Magnetic fields up to $B=45$ T were used to reach filling factor $\nu=1/4$. With the sample situated perpendicular to the applied magnetic field, the diagonal resistance displays a kink at $\nu=1/4$. When the sample is tilted to an angle of $\theta=20.3^{\circ}$, a clear minimum in the diagonal resistance and plateau in the Hall resistance are present at $\nu=1/4$ indicating a fractional quantum Hall state at $\nu=1/4$ in this sample. Several possibilities regarding the origin of this state will also be discussed.