Interaction-disorder-driven characteristic momentum in graphene, approach of multi-body distribution functions

TL;DR

This paper develops a multi-body distribution function approach to analyze disorder and interaction effects in graphene, revealing phenomena like electron-hole puddles, a disorder-driven characteristic momentum, and charge density oscillations at low densities.

Contribution

It introduces a comprehensive framework using multi-point probability measures to study disorder and interactions in graphene, deriving analytical solutions and identifying a disorder-driven characteristic momentum.

Findings

Density fluctuation relates to disorder strength, interaction, and density.

A disorder-driven characteristic momentum $q_{ch}$ emerges in the system.

Charge density oscillations and screening-anti-screening transition occur at low densities.

Abstract

Multi-point probability measures along with the dielectric function of Dirac Fermions in mono-layer graphene containing particle-particle and white-noise (out-plane) disorder interactions on an equal footing in the Thomas-Fermi-Dirac approximation is investigated. By calculating the one-body carrier density probability measure of the graphene sheet, we show that the density fluctuation ($\zeta^{-1}$) is related to the disorder strength ($n_i$), the interaction parameter ($r_s$) and the average density ($\bar{n}$) via the relation $\zeta^{-1}\propto r_sn_i^2\bar{n}^{-1}$ for which $\bar{n}\rightarrow 0$ leads to strong density inhomogeneities, i.e. electron-hole puddles (EHPs), in agreement with the previous works. The general equation governing the two-body distribution probability is obtained and analyzed. We present the analytical solution for some limits which is used for calculating density-density response function. We show that the resulting function shows power-law behaviors in terms of $\zeta$ with fractional exponents which are reported. The disorder-averaged polarization operator is shown to be a decreasing function of momentum like ordinary 2D parabolic band systems. It is seen that a disorder-driven momentum $q_{\text{ch}}$ emerges in the system which controls the behaviors of the screened potential. We show that in small densities an instability occurs in which imaginary part of the dielectric function becomes negative and the screened potential changes sign. Corresponding to this instability, some oscillations in charge density along with a screening-anti-screening transition are observed. These effects become dominant in very low densities, strong disorders and strong interactions, the state in which EHPs appear. The total charge probability measure is another quantity which has been investigated in this paper.