Origin of the quasiuniversality of the minimal conductivity of graphene

Abstract

It is a fact that the minimal conductivity σ0 of most graphene samples is larger than the wellestablished universal value for ideal graphene 4e 2 /πh; in particular, larger by a factor > ∼ π. Despite intense theoretical activity, this fundamental issue has eluded an explanation so far. Here we present fully atomistic quantum mechanical estimates of the graphene minimal conductivity where electronelectron interactions are considered in the framework of density functional theory. We show the first conclusive evidence of the dominant role on the minimal conductivity of charged impurities over ripples, which have no visible effect. Furthermore, in combination with the logarithmic scaling law for diffusive metallic graphene, we ellucidate the origin of the ubiquitously observed minimal conductivity in the range 8e 2 /h > σ0 > ∼ 4e 2 /h.

Magnetism-Dependent Transport Phenomena in Hydrogenated Graphene: From Spin-Splitting to Localization Effects

“…The increase of the conductivity at the Dirac point with respect to the clean limit value 2 G 0 /π has also been theoretically established for Dirac (single-valley) electrons and many types of disorder, being actually observed in most graphene samples . This can be explained by intravalley scattering (dominant over intervalley one) which is induced either by intrinsic (ripples) or extrinsic disorder (charged impurities) always accidentally present in most samples . On the contrary, as soon as quantum interferences come into play in our intentionally disordered systems, σ ↑,↓ ( E , t ) becomes lower than its semiclassical limit, pinpointing the transition to a weak localization regime, as illustrated in Figure (mainframe) for two elapsed times t = 250 fs and t = 2000 fs.…”

“…28 This can be explained by intravalley scattering (dominant over intervalley one) which is induced either by intrinsic (ripples) or extrinsic disorder (charged impurities) always accidentally present in most samples. 29 On the contrary, as soon as quantum interferences come into play in our intentionally disordered systems, σ v,V (E,t) becomes lower than its semiclassical limit, pinpointing the transition to a weak localization regime, as illustrated in Figure 4 (mainframe) for two elapsed times t = 250 fs and t = 2000 fs. From the computed electronic mean free path l e , the corresponding localization length can be estimated using the relationship ξ(E) = l e exp(πσ Drude / 2G 0 ).…”

Conductivity of pure graphene: Theoretical approach using the polarization tensor

“…Theoretically the conductivity of graphene was investigated in many papers using the current-current correlation functions, the Kubo formalism and Boltzmann's transport theory. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] It was noted 11,21 that the values of minimal conductivity obtained by different authors vary depending on the order of limiting transitions used in different theoretical approaches. At the same time, measurements of the conductivity of graphene [29][30][31][32][33] result in somewhat larger values than the theoretical predictions.…”

“…At the same time, measurements of the conductivity of graphene [29][30][31][32][33] result in somewhat larger values than the theoretical predictions. 11,22 During the last few years much attention was attracted also to investigation of the Casimir force between two graphene sheets, a graphene sheet and a plate made of ordinary material and between graphene-coated substrates. In so doing, the density-density correlation functions of graphene in the random phase approximation, the spatially nonlocal dielectric permittivities and other calculation methods have been used.…”

Thermal and electrical transport properties of two-dimensional Dirac graphenylene: a first-principles study

“…According to the PDOS of graphenylene, it can be seen that there are PDOS crossing the Fermi energy level, which also proves the semimetallic characteristics of graphenylene. 46,47 The valence band and conduction band near the Fermi surface mainly come from the contribution of the p z orbitals of C atoms. The unique band structure of graphenylene exhibits a twisted Dirac cone feature at the K point in three-dimensional space (Fig.…”