S. Anissimova

Spin-Independent Origin of the Strongly Enhanced Effective Mass in a Dilute 2D Electron System

We accurately measure the effective mass in a dilute two-dimensional electron system in silicon by analyzing the temperature dependence of the Shubnikov-de Haas oscillations in the low-temperature limit. A sharp increase of the effective mass with decreasing electron density is observed. We find that the enhanced effective mass is independent of the degree of spin polarization, which points to a spin-independent origin of the mass enhancement and is in contradiction with existing theories.

Pauli spin susceptibility of a strongly correlated two-dimensional electron liquid

Thermodynamic measurements reveal that the Pauli spin susceptibility of strongly correlated two-dimensional electrons in silicon grows critically at low electron densities--behavior that is characteristic of the existence of a phase transition.

Magnetization of a strongly interacting two-dimensional electron system in perpendicular magnetic fields.

We measure the thermodynamic magnetization of a low-disordered, strongly correlated two-dimensional electron system in silicon in perpendicular magnetic fields. A new, parameter-free method is used to directly determine the spectrum characteristics (Landé g factor and the cyclotron mass) when the Fermi level lies outside the spectral gaps and the interlevel interactions between quasiparticles are avoided. Intralevel interactions are found to strongly modify the magnetization, without affecting the determined g* and m*.

Thermodynamic magnetization of a strongly correlated two-dimensional electron system

Abstract We measure thermodynamic magnetization of a low-disordered, strongly correlated two-dimensional electron system in silicon. Pauli spin susceptibility is observed to grow critically at low electron densities—behavior that is characteristic of the existence of a phase transition. A new, parameter-free method is used to directly determine the spectrum characteristics (Landeg-factor and the cyclotron mass) when the Fermi level lies outside the spectral gaps and the inter-level interactions between quasiparticles are avoided. It turns out that, unlike in the Stoner scenario, the critical growth of the spin susceptibility originates from the dramatic enhancement of the effective mass, while the enhancement of the g-factor is weak and practically independent of the electron density.

Conductivity of a spin-polarized two-dimensional electron liquid in the ballistic regime

In the ballistic regime, the metallic temperature dependence of the conductivity in a two-dimensional electron system in silicon is found to change non-monotonically with the degree of spin polarization. In particular, it fades away just before the onset of complete spin polarization but reappears again in the fully spin-polarized state, being, however, suppressed relative to the zero-field case. Analysis of the degree of the suppression allows one to distinguish between the screening and the interaction-based theories.

Critical behaviour of the Pauli spin susceptibility of strongly correlated electrons in two dimensions

Thermodynamic measurements reveal that the Pauli spin susceptibility in a strongly correlated low-disorder two-dimensional electron system in silicon becomes enhanced by almost an order of magnitude at low electron densities and has a critical behaviour close to the metal--insulator transition point. This provides thermodynamic evidence for the existence of a phase transition. The nature of the low-density phase still remains unclear because it is masked by the residual disorder in the electron system.