Ground state of graphene heterostructures in the presence of random charged impurities

Rodriguez-Vega, Martin; Fischer, Jonathan; Sarma, S. Das; Rossi, Enrico

doi:10.1103/physrevb.90.035406

Cited by 23 publications

(14 citation statements)

References 74 publications

(165 reference statements)

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“…One possible way to remedy this is to use the rigorous theory presented in Ref. [47] for calculating η and n (A,P ) rms as a function of the system parameters. We leave these as problems for future work.…”

Section: Discussionmentioning

confidence: 99%

Theory of Coulomb drag in spatially inhomogeneous 2D materials

Yudhistira

et al. 2018

Commun Phys

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Coulomb drag between parallel two-dimensional electronic layers is an excellent tool for the study of electron-electron interactions. In actual experiments, the layers display spatial charge density fluctuations due to imperfections such as external charged impurities. However, at present a systematic way of taking these inhomogeneities into account in drag calculations has been lacking, making the interpretation of experimental data problematic. On the other hand, there exists a highly successful and widely accepted formalism describing transport within single inhomogeneous layers known as effective medium theory. In this work, we generalize the standard effective medium theory to the case of Coulomb drag between two inhomogeneous sheets and demonstrate that inhomogeneity in the layers has a strong impact on drag transport. In the case of exciton condensation between the layers, we show that drag resistivity takes on a value determined by the amplitude of density fluctuation. Next we consider drag between graphene sheets, in which the existence of spatial charge density fluctuations is well-known. We show that these inhomogeneities play a crucial role in explaining existing experimental data. In particular, the temperature dependence of the experimentally observed peaks in drag resistivity can only be explained by taking the layer density fluctuations into account. We also propose a method of extracting information on the correlations between the inhomogeneities of the layers. The effective medium theory of Coulomb drag derived here is general and applies to all two-dimensional materials.arXiv:1611.03089v2 [cond-mat.mes-hall]

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Section: Discussionmentioning

confidence: 99%

Theory of Coulomb drag in spatially inhomogeneous 2D materials

Yudhistira

et al. 2018

Commun Phys

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“…To understand screening in this system we carried out numerical simulations that used the Thomas-Fermi-Dirac theory (TFDT) (34,35). In graphene, unlike the case of materials with parabolic bands, the disorder potential created by trapped charges retains its long-range nature (36)(37)(38).…”

Section: Significancementioning

confidence: 99%

Local, global, and nonlinear screening in twisted double-layer graphene

Rodriguez-Vega

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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One-atom-thick crystalline layers and their vertical heterostructures carry the promise of designer electronic materials that are unattainable by standard growth techniques. To realize their potential it is necessary to isolate them from environmental disturbances, in particular those introduced by the substrate. However, finding and characterizing suitable substrates, and minimizing the random potential fluctuations they introduce, has been a persistent challenge in this emerging field. Here we show that Landau-level (LL) spectroscopy offers the unique capability to quantify both the reduction of the quasiparticles' lifetime and the long-range inhomogeneity due to random potential fluctuations. Harnessing this technique together with direct scanning tunneling microscopy and numerical simulations we demonstrate that the insertion of a graphene buffer layer with a large twist angle is a very effective method to shield a 2D system from substrate interference that has the additional desirable property of preserving the electronic structure of the system under study. We further show that owing to its remarkable nonlinear screening capability a single graphene buffer layer provides better shielding than either increasing the distance to the substrate or doubling the carrier density and reduces the amplitude of the potential fluctuations in graphene to values even lower than the ones in AB-stacked bilayer graphene.he recent realization of one-atom-thick layers and the fabrication of layered Van der Waals heterostructures revealed fascinating physical phenomena and novel devices based on interlayer interactions (1-10). Inherent to the 2D structure of these layers is an extreme vulnerability to disturbances introduced by the substrate (11)(12)(13)(14). Substrate interference can be eliminated by suspending the sample, an approach that led to the observation of ballistic transport (15, 16) and the fractional quantum Hall effect in graphene (17)(18)(19)(20), but this method only works for small (micrometer-sized) samples at relatively low doping. Another approach is to use atomically smooth metallic substrates (21-23) or graphite (24-28), which screen the random potential. However, these substrates short-circuit the 2D channel and prevent tuning the carrier density by gating, rendering them unsuitable for device applications. Among insulating substrates atomically flat hBN (29-31) and MoS 2 (6) have recently emerged as promising alternatives to SiO 2 substrates.Here we show that by inserting a graphene buffer layer between the 2D sample (in this case, also graphene) and the insulating substrate, the random potential fluctuations are screened without compromising the electronic structure of the 2D system under study and the gating capability. This capability relies on the fact that in van der Waals structures the stacking configuration in the third direction can be set arbitrarily and is not fixed by the chemistry of the elements forming the heterostructure. Consequently it is possible to electronically decouple two 2D cry...

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“…We see that the presence of SLG or BLG significantly increases the quasiparticle lifetime, even in the limit when the interlayer tunneling between the TI and SLG (BLG) is zero. This is due to the additional screening in the presence of SLG or BLG which affects the disorder potential created by the charge impurities . We expect that such an increase in the quasiparticle lifetime will lead to enhancements in some of the spin‐dependent transport phenomena.…”

Section: Graphene‐ti Heterostructuresmentioning

confidence: 99%

“…This is due to the additional screening in the presence of SLG or BLG which affects the disorder potential created by the charge impurities. [81,92] We expect that such an increase in the quasiparticle lifetime will lead to enhancements in some of the spin-dependent transport phenomena. Similarly, by including the [1 − k ⋅ (k + q)] under the sum on the right hand side of Equation (13) we can obtain the transport time ta (k), and then, after averaging over the bands at the Fermi energy, the corresponding average ⟨ t ⟩.…”

Section: Transport Propertiesmentioning

confidence: 99%

Van Der Waals Heterostructures with Spin‐Orbit Coupling

Rossi

Triola

2019

Annalen der Physik

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Herein, recent work on van der Waals (vdW) systems in which at least one of the components has strong spin‐orbit coupling is reviewed, focussing on a selection of vdW heterostructures to exemplify the type of interesting electronic properties that can arise in these systems. First a general effective model to describe the low energy electronic degrees of freedom in these systems is presented. The model is then applied to study the case of (vdW) systems formed by a graphene sheet and a topological insulator. The electronic transport properties of such systems are discussed and it is shown how they exhibit much stronger spin‐dependent transport effects than isolated topological insulators. Then, vdW systems are considered in which the layer with strong spin‐orbit coupling is a monolayer transition metal dichalcogenide (TMD) and graphene‐TMD systems are briefly discussed. In the second part of the article, a case is discussed in which the vdW system includes a superconducting layer in addition to the layer with strong spin‐orbit coupling. It is shown in detail how these systems can be designed to realize odd‐frequency superconducting pair correlations. Finally, twisted graphene‐NbSe2 bilayer systems are discussed as an example in which the strength of the proximity‐induced superconducting pairing in the normal layer, and its Ising character, can be tuned via the relative twist angle between the two layers forming the heterostructure.

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Ground state of graphene heterostructures in the presence of random charged impurities

Cited by 23 publications

References 74 publications

Theory of Coulomb drag in spatially inhomogeneous 2D materials

Theory of Coulomb drag in spatially inhomogeneous 2D materials

Local, global, and nonlinear screening in twisted double-layer graphene

Van Der Waals Heterostructures with Spin‐Orbit Coupling

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