Adbhut Gupta

The even-denominator fractional quantum Hall states (FQHSs) in half-filled Landau levels have garnered interest due to potential use in topological quantum computing, owing to their possible non-Abelian nature. Of particular interest is the competition and interplay between the even-denominator FQHSs and other ground states, such as anisotropic phases and composite fermion Fermi seas. We present the observation of an even-denominator fractional quantum Hall state with highly anisotropic in-plane transport coefficients at Landau level filling factor ν = 3/2 in an ultra-high-quality GaAs two-dimensional hole system under the influence of an in-plane magnetic field. We observe a sharp transition from an isotropic composite fermion Fermi sea to an anisotropic even-denominator FQHS with increasing in-plane magnetic field. Our data and calculations suggest that coupling between heavy-hole and light-hole states combines different orbital components in the wavefunction of one Landau level, and leads to the emergence of a highly-anisotropic even-denominator FQHS. This feature is unique to two-dimensional holes, making them an attractive platform for exploring exotic, many-body phenomena.