Critical temperature and Ginzburg region near a quantum critical point in two-dimensional metals

We compute the transition temperature T-c and the Ginzburg temperature T-G above T-c near a quantum critical point at the boundary of an ordered phase with a broken discrete symmetry in a two-dimensional metallic electron system. Our calculation is based on a renormalization group analysis of the Hertz action with a scalar order parameter. We provide analytic expressions for T-c and T-G as a function of the nonthermal control parameter for the quantum phase transition, including logarithmic corrections. The Ginzburg regime between T-c and T-G occupies a sizable part of the phase diagram.