Record-quality two-dimensional electron systems

We present our recent results on the growth of record-quality GaAs quantum wells via molecular beam epitaxy (MBE). These results were achieved by a careful purification and assessment of source material and vacuum quality, as well as innovation in MBE chamber design. Two-dimensional electron systems (2DESs) hosted in our new samples have a factor of ~2 higher mobility than the best previous 2DESs, with a peak mobility of electrons to μ = 44×10⁶ cm²/Vs at an electron density of only n = 2×10¹¹ /cm². This is the highest mobility observed in any material. In representative samples with n ≈ 1×10¹¹ /cm², low temperature magnetotransport data display many-body states that have never been seen before. Furthermore, we find that the robustness of exotic interaction-driven states in these samples is unprecedented. For example, the ν = 5/2 fractional quantum Hall state shows an extraordinarily large activation gap of Δ = 820 mK, significantly larger than the previous record value of ~620 mK in samples with much larger electron densities of n ≈ 3×10¹¹ /cm².

Reference: Yoon Jang Chung, K. A. Villegas-Rosales, K. W. Baldwin, P. T. Madathil, K. W. West, M. Shayegan, L. N. Pfeiffer, arXiv:2010.02283.