Atomistic T -matrix theory of disordered two-dimensional materials: Bound states, spectral properties, quasiparticle scattering, and transport

Abstract

In this work, we present an atomistic first-principles framework for modeling the low-temperature electronic and transport properties of disordered two-dimensional (2D) materials with randomly distributed point defects (impurities). The method is based on the T -matrix formalism in combination with realistic density-functional theory (DFT) descriptions of the defects and their scattering matrix elements. From the T -matrix approximations to the disorder-averaged Green's function (GF) and the collision integral in the Boltzmann transport equation, the method allows calculations of, e.g., the density of states (DOS) including contributions from bound defect states, the quasiparticle spectrum and the spectral linewidth (scattering rate), and the conductivity/mobility of disordered 2D materials. We demonstrate the method by examining these quantities in monolayers of the archetypal 2D materials graphene and transition metal dichalcogenides (TMDs) contaminated with vacancy defects and substitutional impurity atoms. By comparing the Born and T -matrix approximations, we also demonstrate a strong breakdown of the Born approximation for defects in 2D materials manifested in a pronounced renormalization of, e.g., the scattering rate by the higherorder T -matrix method. As the T -matrix approximation is essentially exact for dilute disorder, i.e., low defect concentrations (c dis 1) or density (n dis A −1 cell where A cell is the unit cell area), our first-principles method provides an excellent framework for modeling the properties of disordered 2D materials with defect concentrations relevant for devices. arXiv:1911.00530v1 [cond-mat.mes-hall] 1 Nov 2019

Electron and hole transport in disordered monolayerMoS2: Atomic vacancy induced short-range and Coulomb disorder scattering

“…which is recovered for weak disorder. Also, the above is in contrast to the situation for vacancies in graphene where the scattering rate is predicted to have a nonmonotonic energy dependence due to resonance scattering off quasibound defect states in the vicinity of the Dirac point [80][81][82][83][84].…”

“…(10), we have used the atomistic method outlined in Refs. [42,84] to calculate the T matrix for atomic 115409-4 vacancies in 2D MoS 2 based on Eq. (6) with DFT inputs for the band structure (including spin-orbit interaction) and defect matrix elements sampled in the entire BZ [75].…”

Signatures of adatom effects in the quasiparticle spectrum of Li-doped graphene

“…In this work, we study the spectral properties of disordered Li@graphene, i.e., graphene with a random configuration of Li adatoms as illustrated in Fig. 1(a), using an atomistic first-principles T -matrix formalism based on a parameter-free description of the impurity potential [30,31]. This allows for a detailed description of (i) the spectral Γ-point feature including its hitherto unexplored concentration dependence as well as (ii) the renormalization and linewidth broadening of the bands due to adatom-induced quasiparticle (QP) scattering.…”

“…In the following, we obtain the GF and spectral function of Li@graphene based on atomistic DFT (LCAO) calculations [42] of the band structure and impurity matrix elements sampled in the full BZ using the atomistic method described in Refs. [30,31] (see Ref. [46] for recent related developments).…”

“…3(a)]. For clarity, we have separated out the contributions from intravalley (left) and intervalley (right) scattering using the optical theorem [31,54]. At energies below ∼ 1 eV, the intravalley rate exceeds the intervalley rate by far.…”