Sharp increase of the effective mass near the critical density in a metallic two-dimensional electron system

We find that at intermediate temperatures, the metallic temperature dependence of the conductivity σ(T) of two-dimensional electrons in silicon is described well by a recent interaction-based theory of Zala et al. [Phys. Rev. B 64, 214204 (2001)]. The tendency of the slope σ^-1dσ/dT to diverge near the critical electron density is in agreement with the previously suggested ferromagnetic instability in this electron system. Comparing theory and experiment, we arrive at a conclusion that the instability, unexpectedly, originates from the sharp enhancement of the effective mass, while the effective Land\'e g factor remains nearly constant and close to its value in bulk silicon.