Understanding limits to mobility in ultrahigh-mobility GaAs two-dimensional electron systems: 100 million cm2/Vs and beyond

For several decades now, ultrahigh-mobility GaAs two-dimensional electron systems (2DESs) have served as the hallmark platform for various branches of research in condensed-matter physics. Fundamental to this long-standing history of success for GaAs 2DESs was continuous sample quality improvement, which enabled scattering-free transport over macroscopic lengthscales as well as the emergence of a diverse range of exotic many-body phenomena. While the recent breakthrough in the quality of GaAs 2DESs grown by molecular beam epitaxy is highly commendable in this context, it is also important and timely to establish an up-to-date understanding of what obstructs us from pushing the mobility limit even further. Here, we present mobility data taken at a temperature of 0.3 K for a wide variety of state-of-the-art GaAs 2DESs, exhibiting a maximum, world-record mobility of μ≃57×106cm2/Vs at a 2DES density of n=1.55×1011/cm2. We also provide comprehensive analyses of the collective scattering mechanisms that can explain the results. Furthermore, based on our study, we discuss potential scenarios in which GaAs 2DES mobility values exceeding 100×106cm2/Vs could be achieved.