The valley splitting, which lifts the degeneracy of the lowest two valley states in a SiO2/Si(100)/SiO2 quantum well, is examined through transport measurements. We demonstrate that the valley splitting can be observed directly as a step in the conductance defining a boundary between valley-unpolarized and -polarized regions. This persists to well above liquid helium temperature and shows no dependence on magnetic field, indicating that single-particle valley splitting and valley polarization exist in (100) silicon even at zero magnetic field.
Takashina, K., Ono, Y., Fujiwara, A., Takahashi, Y., & Hirayama, Y. (2006). Valley polarization in Si(100) at zero magnetic field. Physical Review Letters, 96(23), . https://doi.org/10.1103/PhysRevLett.96.236801