We report magnetotransport measurements of fractional quantum Hall states in an AlAs quantum well around Landau level filling factor nu = 3/2, demonstrating that the quasiparticles are composite Fermions (CFs) with a valley degree of freedom. By monitoring the valley level crossings for these states as a function of applied symmetry-breaking strain, we determine the CF valley susceptibility and polarization. The data can be explained well by a simple Landau level fan diagram for CFs, and are in nearly quantitative agreement with the results reported for CF spin polarization.
@article{arxiv.0706.1195,
title = {Valley polarization and susceptibility of composite fermions around nu=3/2},
author = {N. C. Bishop and M. Padmanabhan and K. Vakili and Y. P. Shkolnikov and E. P. De Poortere and M. Shayegan},
journal= {arXiv preprint arXiv:0706.1195},
year = {2009}
}