Valleytronics is rapidly emerging as an exciting area of basic and applied research. In two dimensional systems, valley polarisation can dramatically modify physical properties through electron-electron interactions as demonstrated by such phenomena as the fractional quantum Hall effect and the metal-insulator transition. Here, we address the electrons' spin alignment in a magnetic field in silicon-on-insulator quantum wells under valley polarisation. In stark contrast to expectations from a non-interacting model, we show experimentally that less magnetic field can be required to fully spin polarise a valley-polarised system than a valley-degenerate one. Furthermore, we show that these observations are quantitatively described by parameter free ab initio quantum Monte Carlo simulations. We interpret the results as a manifestation of the greater stability of the spin and valley degenerate system against ferromagnetic instability and Wigner crystalisation which in turn suggests the existence of a new strongly correlated electron liquid at low electron densities.
@article{arxiv.1506.01813,
title = {Valley polarization assisted spin polarization in two dimensions},
author = {V. T. Renard and B. A. Piot and X. Waintal and G. Fleury and D. Cooper and Y. Niida and D. Tregurtha and A. Fujiwara and Y. Hirayama and K. Takashina},
journal= {arXiv preprint arXiv:1506.01813},
year = {2015}
}