Coherent potential approximation for spatially correlated disorder

TL;DR

This paper extends the coherent potential approximation (CPA) to handle spatially correlated, smoothly varying disorder, maintaining simplicity while improving accuracy, and applies it to excitonic spectra across dimensions.

Contribution

The authors develop a simplified, accurate CPA extension for correlated disorder that preserves the single self-energy framework, unlike previous cluster methods.

Findings

The extended CPA accurately matches exact Green's function moments.

It successfully reproduces spectral functions from numerical simulations.

The method effectively models excitonic absorption spectra in various dimensions.

Abstract

The coherent potential approximation (CPA) is extended to describe satisfactorily the motion of particles in a random potential which is spatially correlated and smoothly varying. In contrast to existing cluster-CPA methods, the present scheme preserves the simplicity of the conventional CPA in using a single self-energy function. Its accuracy is checked by a comparison with the exact moments of the Green's function, and with the spectral function from numerical simulations. The scheme is applied to excitonic absorption spectra in different spatial dimensions.