Revisiting the Thomas-Fermi Potential for Three-Dimensional Condensed Matter Systems

TL;DR

This paper introduces a probabilistic method to evaluate the validity of the Thomas-Fermi potential in 3D condensed matter systems, revealing its accuracy at high densities but potential errors at lower densities.

Contribution

A formally exact probabilistic approach based on the radial Schrödinger equation to assess Thomas-Fermi potential validity in condensed matter systems.

Findings

Thomas-Fermi approximation valid at high electron densities

Probability density profiles are similar across different materials at high densities

Potential errors in observables when applying the approximation to GaAs at zero temperature

Abstract

We proposed a formally exact, probabilistic method to assess the validity of the Thomas-Fermi potential for three-dimensional condensed matter systems where electron dynamics is constrained to the Fermi surface. Our method, which relies on accurate solutions of the radial Schr\"{o}dinger equation, yields the probability density function for momentum transfer. This allows for the computation of its expectation values, which can be compared with unity to confirm the validity of the Thomas-Fermi approximation. We applied this method to three {\it n}-type direct-gap III-V model semiconductors (GaAs, InAs, InSb) and found that the Thomas-Fermi approximation is certainly valid at high electron densities. In these cases, the probability density function exhibits the same profile, irrespective of the material under scrutiny. Furthermore, we show that this approximation can lead to serious errors in the computation of observables when applied to GaAs at zero temperature for most electron densities under scrutiny.