title: Ferromagnetic fractional quantum Hall states in a valley-degenerate two-dimensional electron system.
abstract: We study a two-dimensional electron system where the electrons occupy two conduction band valleys with anisotropic Fermi contours and strain-tunable occupation. We observe persistent quantum Hall states at filling factors nu=1/3 and 5/3 even at zero strain when the two valleys are degenerate. This is reminiscent of the quantum Hall ferromagnet formed at nu=1 in the same system at zero strain. In the absence of a theory for a system with anisotropic valleys, we compare the energy gaps measured at nu=1/3 and 5/3 to the available theory developed for single-valley, two-spin systems, and find that the gaps and their rates of rise with strain are much smaller than predicted.
authors.affiliation: Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Medini
authors.initials: M
authors.lastname: Padmanabhan
authors.forename: T
authors.initials: T
authors.lastname: Gokmen
authors.forename: M
authors.initials: M
authors.lastname: Shayegan