Observation of Fractional Quantum Hall Effect in an InAs Quantum Well*

The InAs two-dimensional electron system is one of the prime candidates for hosting exotic quasiparticles such as Majorana fermions and parafermions that exhibit non-Abelian statistics. To fulfill its full promise, however, the system must be clean enough to show evidence of electron-electron interaction. Here we study a very low disorder, 24-nm-wide InAs quantum well with density of 7.8 × 10¹¹ cm^-2 and low-temperature mobility 1.8 × 10⁶ cm²/Vs. The sample exhibits resolvable Shubnikov de Haas oscillations at magnetic field as low as ≈ 0.5 T (v = 68) and becomes spin-resolved at B > 0.9 T (v ≤ 37). At a temperature of ≈ 35 mK and B ≈ 24 T, we observe a deep minimum in longitudinal resistance, accompanied by a nearly quantized Hall plateau at filling factor v = 4/3. This observation places the InAs two-dimensional electron system among the few systems that exhibit fractional quantum Hall effect, and it is an important step towards the realization of exotic quasi-particles, such as parafermions, that are required for universal quantum computation.