The energy scale behind the metallic behaviors in low-density Si-MOSFETs

TL;DR

This paper demonstrates that the metallic behavior in low-density Si-MOSFETs is governed by a polarization energy scale, with quantum calculations aligning with experimental data, suggesting a potential transition to insulating behavior at very low temperatures.

Contribution

It identifies the polarization energy as the key scale controlling metallic behavior in Si-MOSFETs and provides ab-initio calculations that match experimental observations without adjustable parameters.

Findings

Polarization energy matches experimental characteristic energies.

Metallic behavior may transition to insulating at low temperatures.

Quantum Monte Carlo calculations agree with resistivity data.

Abstract

We show that the unexpected metallic behavior (the so-called two-dimensional metal-insulator transition) observed in low-density Silicon metal-oxide-semiconductor field-effect transistors (Si-MOSFETs) is controlled by a unique characteristic energy scale, the polarization energy. On one hand, we perform Quantum Monte Carlo calculations of the energy needed to polarize the two dimensional electron gas at zero temperature, taking into account Coulomb interactions, valley degeneracy and electronic mobility (disorder). On the other hand, we identify the characteristic energy scale controlling the physics in eight different sets of experiments. We find that our {\it ab-initio} polarization energies (obtained without any adjustable parameters) are in perfect agreement with the observed characteristic energies for all available data, both for the magnetic field and temperature dependence of the resistivities. Our results put strong constraints on possible mechanisms responsible for the metallic behavior. In particular, there are strong indications that the system would eventually become insulating at low enough temperature.