We report experimental results on a quantum point contact (QPC) device formed in a wide AlAs quantum well where the two-dimensional electrons occupy two in-plane valleys with elliptical Fermi contours. To probe the closely-spaced, one-dimensional electric subbands, we fabricated a point contact device defined by shallow-etching and a top gate that covers the entire device. The conductance versus top gate bias trace shows a series of weak plateaus at integer multiples of 2e2/h, indicating a broken valley degeneracy in the QPC and implying the potential use of QPC as a simple "valley filter" device. A model is presented to describe the quantized energy levels and the role of the in-plane valleys in the transport. We also observe a well-developed conductance plateau near 0.7x2e2/h which may reflect the strong electron-electron interaction in the system.
@article{arxiv.cond-mat/0606272,
title = {Quantized conductance in an AlAs 2D electron system quantum point contact},
author = {O. Gunawan and B. Habib and E. P. De Poortere and M. Shayegan},
journal= {arXiv preprint arXiv:cond-mat/0606272},
year = {2009}
}