We report here a systematic study of the energy gaps at the odd-integer quantum Hall states ν=3 and 5 under tilted magnetic (B) fields in a high quality Si two-dimensional electron system. Out of the coincidence region, the valley splitting is independent of the in-plane B fields. However, the ν=3 valley gap differs by about a factor of 3 (Δv∼ 0.4K vs. 1.2K) at either side of the coincidence. More surprisingly, instead of reducing to zero, the energy gaps at ν=3 and 5 rise rapidly when approaching the coincidence angles. We believe that such anomaly is related to strong coupling of the nearly degenerate Landau levels.
@article{arxiv.cond-mat/0510599,
title = {Observation of Inter-Valley Gap Anomaly of Two Dimensional electrons in Silicon},
author = {K. Lai and W. Pan and D. C. Tsui and S. Lyon and M. Mühlberger and F. Schäffler},
journal= {arXiv preprint arXiv:cond-mat/0510599},
year = {2007}
}