The effective mass and the g - factor of the strongly - correlated 2 - D electron fluid .

Europhysics Letters PREPRINT The effective mass and the g-factor of the strongly-correlated 2-D electron fluid. Evidence for a coupled-valley state in the Si system. Abstract. – The effective mass m * , and the Landé g-factor of the uniform 2-D electron system (2DES) are calculated as a function of the spin polarization ζ, and the density parameter rs, using a non-perturbative analytic approach. Our theory is in good accord with the susceptibility data for the simple 2DES, and in excellent agreement with the two-valley Si-2DES data of Shashkin et al. While g * is enhanced in GaAs, m * is enhanced in Si. The two-valley susceptibility is treated within a coupled-mode (coupled-valley) approach. The coupled-valley model is confirmed by comparison with the Quantum Monte Carlo results for a 4-component 2DES. The 2-D electron fluid (2DES) exhibits a wealth of intriguing physics, straddling a rich phase diagram [1,2]. The phase diagram contains spin-polarized states at sufficiently large r s , say ∼ 20 − 27. Here r s = (πn) −1/2 is the electron-disk radius [3, 4] at the density n, in atomic units. It is also equal to the value of the coupling constant Γ = (potential energy)/(kinetic energy). The intermediate regime r s ∼ 5 − 20 also hosts many ill-understood phenomena including the metal-insulator transition (MIT) [5]. Anomalous values (e.g, see [6]), of g * and m * have been found. Some experiments suggest that an enhancement of g * is responsible for the strong enhancement of m * g * , while results [7] on Si metal-oxide field effect transistors (MOSFETs) suggest that it is m * , and not g * which is enhanced. In this study we show that, for ideally thin 2-D layers. g * is enhanced in GaAs-like systems, while m * is enhanced in Si-like multi-valley systems. The existence of a coupled-valley state follows naturally from the physics of the Si system, and here we present a model leading to excellent quantitative agreement with experiment, and with Quantum Monte Carlo (QMC) simulations of a 4-component 2DES [8]. Fermi liquid-type theories [9] are valid for r s < 1. Such perturbative methods have been applied, invoking impurities [10], or charge and spin-density wave effects [11]. On the other hand, QMC calculations of m * involve the excited states of the 2DES and are less reliable than for the ground state. QMC results up …