Superconductivity in a two-dimensional Electron Gas: Application to a Si MOSFET

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  • 11 February 1998
Abstract
Kravchenko and colleagues recently reported the existence of an insulator-metal transition (IMT) in two-dimensional (2D) high mobility Si MOSFET's. These results are surprising because it is generally accepted that such a transition is strictly forbidden in two dimensions, at least in the absence of electron interactions. We analyse this transition in the context of the frequency-dependent dielectric function ($\epsilon(q,\omega)$) for a dilute 2D electron gas. In the range of densities ($r_s\sim 10$) relevant to the experiments, we show that plasma excitations lead to a sign change of the dielectric function that persists over a wide range of frequencies and momenta. We solve the weak-coupling gap equations with the bare electron interactions scaled by \epsilon(q,\omega) and illustrate that correlation-hole effects can enhance the mean-field superconducting transition temperature, T_c, by a factor of 10^3 over standard perturbative treatments of the electron gas. We also show that the magneto-resistance data exhibits scaling in the vicinity of a critical field of 9.5kOe. The presence of a critical field on the order of the mean-field T_c (.4K) predicted here lends credence to the interpretation of the conducting phase as a superconducting one.

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