Observation of a Fractional Quantum Hall State atν=1/4in a Wide GaAs Quantum Well

Abstract

We report the observation of an even-denominator fractional quantum Hall state at $\nu =1/4$ in a high quality, wide GaAs quantum well. The sample has a quantum well width of 50 nm and an electron density of $n_e=2.55\times {10}^{11}{\mathrm{cm}}^{-2}$. We have performed transport measurements at $T\sim 35\mathrm{mK}$ in magnetic fields up to 45 T. When the sample is perpendicular to the applied magnetic field, the diagonal resistance displays a kink at $\nu =1/4$. Upon tilting the sample to an angle of $\theta =20.3°$ a clear fractional quantum Hall state emerges at $\nu =1/4$ with a plateau in the Hall resistance and a strong minimum in the diagonal resistance.