Degenerate conduction-band minima, or `valleys', in materials such as Si, AlAs, graphene, and MoS2 allow them to host two-dimensional electron systems (2DESs) that can access a valley degree of freedom. These multivalley 2DESs present exciting opportunities for both pragmatic and fundamental research alike because not only are they a platform for valleytronic devices, but they also provide a tool to tune and investigate the properties of complex many-body ground states. Here, we report ultra-high quality, modulation doped AlAs quantum wells containing 2DESs that occupy two anisotropic valleys and have electron mobilities peaking at 2.4×106 cm2V−1s−1 at a density of 2.2×1011 cm−2. This is more than an order of magnitude improvement in mobility over previous results. The unprecedented quality of our samples is demonstrated by magneto-transport data that show high-order fractional quantum Hall minima up to the Landau level filling ν=8/17, and even the elusive ν=1/5 quantum Hall state.
@article{arxiv.1807.11563,
title = {Multivalley two-dimensional electron system in an AlAs quantum well with mobility exceeding $2\times10^6$ cm$^{2}$V$^{-1}$s$^{-1}$},
author = {Yoon Jang Chung and K. A. Villegas Rosales and H. Deng and K. W. Baldwin and K. W. West and M. Shayegan and L. N. Pfeiffer},
journal= {arXiv preprint arXiv:1807.11563},
year = {2018}
}