title: Valley polarization assisted spin polarization in two dimensions.
abstract: Valleytronics is rapidly emerging as an exciting area of basic and applied research. In two-dimensional systems, valley polarization 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 polarization. In stark contrast to expectations from a non-interacting model, we show experimentally that less magnetic field can be required to fully spin polarize a valley-polarized 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 crystalization, which in turn suggests the existence of a new strongly correlated electron liquid at low electron densities.
authors.affiliation: Université Grenoble Alpes/CEA, INAC-SPSMS, F-38000, Grenoble, France.
authors.forename: V T
authors.initials: VT
authors.lastname: Renard
authors.affiliation: Laboratoire National des Champs Magnétiques Intenses, CNRS-UJF-UPS-INSA-EMFL, 38042, Grenoble, France.
authors.forename: B A
authors.initials: BA
authors.lastname: Piot
authors.affiliation: Université Grenoble Alpes/CEA, INAC-SPSMS, F-38000, Grenoble, France.
authors.forename: X
authors.initials: X
authors.lastname: Waintal
authors.affiliation: Service de Physique de l'État Condensé, DSM/IRAMIS/SPEC, CNRS UMR 3680 CEA Saclay, 91191 Gif sur Yvette, France.
authors.forename: G
authors.initials: G
authors.lastname: Fleury
authors.affiliation: Université Grenoble Alpes/CEA Leti Minatec campus, F-38054, Grenoble, France.
authors.forename: D
authors.initials: D
authors.lastname: Cooper
authors.affiliation: Graduate School of Science, Tohoku University, 6-3 Aramakiaza Aoba, Aobaku, Sendai, 980-8578, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Niida
authors.affiliation: Department of Physics, University of Bath, Bath, BA2 7AY, UK.
authors.forename: D
authors.initials: D
authors.lastname: Tregurtha
authors.affiliation: NTT Basic Research Laboratories, NTT Corporation, Atsugi-shi, Kanagawa, 243-0198, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Fujiwara
authors.affiliation: Graduate School of Science, Tohoku University, 6-3 Aramakiaza Aoba, Aobaku, Sendai, 980-8578, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Hirayama
authors.affiliation: Department of Physics, University of Bath, Bath, BA2 7AY, UK.
authors.forename: K
authors.initials: K
authors.lastname: Takashina