We report anomalous structure in the magnetoresistance of SiO2/Si(100)/SiO2 quantum wells. When Landau levels of opposite valleys are driven through coincidence at the Fermi level, the longitudinal resistance displays elevations at filling factors that are integer multiples of 4 (ν=4i) accompanied by suppression on either side of ν=4i. This persists when either magnetic field or valley splitting is swept leading to resistance ridges running along ν=4i. The range of field over which they are observed points to the role of spin degeneracy, which is directly confirmed by their disappearance under in-plane magnetic field. The data suggest a new type of many-body effect due to the combined degeneracy of valley and spin.
Cite
@article{arxiv.cond-mat/0611662,
title = {Anomalous Resistance Ridges Along Filling Factor $\nu = 4i$},
author = {K. Takashina and M. Brun and T. Ota and D. K. Maude and A. Fujiwara and Y. Ono and Y. Takahashi and Y. Hirayama},
journal= {arXiv preprint arXiv:cond-mat/0611662},
year = {2009}
}