Scaling of the magnetoconductivity of silicon MOSFETs: Evidence for a quantum phase transition in two dimensions

For a broad range of electron densities n and temperatures T, the in-plane magnetoconductivity of the two-dimensional system of electrons in silicon MOSFETs can be scaled onto a universal curve with a single parameter H-sigma(n, T), where H-sigma obeys the empirical relation H-sigma = A(n) [Delta (n)(2) + T-2](1/2). The characteristic energy k(B)Delta associated with the magnetic field dependence of the conductivity decreases with decreasing density, and extrapolates to 0 at a critical density n(0), signaling the approach to a zero-temperature quantum phase transition. We show that H-sigma = AT for densities near n(0).