title: Two-flux composite fermion series of the fractional quantum Hall states in strained Si.
abstract: Magnetotransport properties are investigated in a high-mobility two-dimensional electron system in the strained Si quantum well of a (100) Si(0.75)Ge(0.25)/Si/Si(0.75)Ge0.25 heterostructure, at temperatures down to 30 mK and in magnetic fields up to 45 T. We observe around nu=1/2 the two-flux composite fermion (CF) series of the fractional quantum Hall effect (FQHE) at nu=2/3, 3/5, 4/7, and at nu=4/9, 2/5, 1/3. Among these FQHE states, the nu=1/3, 4/7, and 4/9 states are seen for the first time in the Si/SiGe system. Interestingly, of the CF series, the 3/5 state is weaker than the nearby 4/7 state and the 3/7 state is conspicuously missing, resembling the observation in the IQHE regime that the nu=3 is weaker than the nearby nu=4 state. Our results can be quantitatively understood in the picture of CF's with the valley degree of freedom.
authors.affiliation: Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: K
authors.initials: K
authors.lastname: Lai
authors.forename: W
authors.initials: W
authors.lastname: Pan
authors.forename: D C
authors.initials: DC
authors.lastname: Tsui
authors.forename: S
authors.initials: S
authors.lastname: Lyon
authors.forename: M
authors.initials: M
authors.lastname: Mühlberger
authors.forename: F
authors.initials: F
authors.lastname: Schäffler