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

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We report the observation of an even-denominator fractional quantum Hall (FQH) 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 $n_e=2.55\times10^{11}$ cm$^{-2}$.
• We have performed transport measurements at $T\sim35$ 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 $\nu=1/4$.