Dislocation and node states in bilayer graphene systems

Weckbecker, D.; Gupta, R.; Rost, F.; Sharma, S.; Shallcross, S.

doi:10.1103/physrevb.99.195405

Cited by 8 publications

(4 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…for a twist bilayer the AB or AA stacked bilayer), and |φ X corresponding plane wave states. This approach has been fully described in 27 , and used to treat optical deformations in graphene in 28 , and partial dislocations in bilayer graphene in 19,20,30 . In what follows we describe in overview the methodology, in particular how it pertains to lattice relaxation in the twist bilayer, but refer the reader to these references for further details.…”

Section: B Model Relaxation Fieldmentioning

confidence: 99%

Perfect and Controllable Nesting in Minimally Twisted Bilayer Graphene

et al. 2019

View full text Add to dashboard Cite

Parallel ("nested") regions of a Fermi surface (FS) drive instabilities of the electron fluid, for example the spin density wave in elemental chromium. In one-dimensional materials, the FS is trivially fully nested (a single nesting vector connects two "Fermi dots"), while in higher dimensions only a fraction of the FS consists of parallel sheets. We demonstrate that the tiny angle regime of twist bilayer graphene (TBLG) possess a phase, accessible by interlayer bias, in which the FS consists entirely of nestable "Fermi lines": the first example of a completely nested FS in a 2d material. This nested phase is found both in the ideal as well as relaxed structure of the twist bilayer. We demonstrate excellent agreement with recent STM images of topological states in this material and elucidate the connection between these and the underlying Fermiology. We show that the geometry of the "Fermi lines" network is controllable by the strength of the applied interlayer bias, and thus that TBLG offers unprecedented access to the physics of FS nesting in 2d materials. 1 arXiv:1908.08318v1 [cond-mat.mtrl-sci] 22 Aug 2019 of the FS consists of nested sheets) and notoriously difficult to control 10,11 . In contrast, the nesting exhibited by the twist bilayer is both complete (100% nested) and, as we show, can be fully controlled by tuning of the interlayer bias.This "nesting phase" of the twist bilayer is found in a large regime of angle-field space and is, remarkably, found both for the ideal twist geometry as well as the structural dislocation network that it reconstructs to at tiny angles 12-14 . The finding of a robust moiré-induced 2d "Fermi line" analogy of the 1d "Fermi dot" topology, controllable via bias, both offers unprecedented access to the physics of FS nesting, as well as highlighting the remarkable electronic structures that can be created by moiré geometries and their structural dislocation networks in 2d materials. II. RESULTS A. ModelThe physics of the tiny angle regime of the twist bilayer is an essentially multiscale problem involving both the lattice constant of graphene -the scale at which atomic relaxation 2 FIG. 1: Fully nested Fermiology in the graphene twist bilayer and the corresponding dislocation network (θ = 0.51 • , E = 90 mV/Å). Below ∼ 1 • twist bilayer graphene relaxes into an ordered network of dislocations, with the smoothly varying stacking order of the ideal twist geometry (a) becoming series of sharp AB and BA domains (b), each separated by pure shear partial dislocations with high von Mises strain (J 2 ) (c,d). Pseudo-magnetic fields of the order of 40 T are induced in the AB and BA regions with alternating sign between the latter (e,f). In the density of states (DOS) the zero mode is substantially broadened, with the valley region shifting upwards in energy (g).However, while atomic relaxation induces dramatic changes to the Fermiology in the zero mode region (l,m), in the valley region a remarkably stable Fermi topology of fully nested Fermi lines is seen (nesting vector indicated by...

show abstract

Section: B Model Relaxation Fieldmentioning

confidence: 99%

Perfect and Controllable Nesting in Minimally Twisted Bilayer Graphene

et al. 2019

View full text Add to dashboard Cite

show abstract

“…For further details we refer the reader to Ref. 20 as well as several applications of the method: to minimally twisted bilayer graphene 18 , partial dislocation networks [21][22][23] , and in-plane deformation fields 24,25 .…”

Section: Effective Hamiltonian Theorymentioning

confidence: 99%

A general relation between stacking order and Chern index: a topological map of minimally twisted bilayer graphene

Theil,

Fleischmann,

Gupta

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

We derive a general relation between the stacking vector u describing the relative shift of two layers of bilayer graphene and the Chern index. We find C = ν − sign (|VAB| − |VBA|), where ν is a valley index and |V αβ | the absolute value of stacking potentials that depend on u and that uniquely determine the interlayer interaction; AA stacking plays no role in the topological character. With this expression we show that while ideal and relaxed minimally twisted bilayer graphene appear so distinct as to be almost different materials, their Chern index maps are, remarkably, identical. The topological physics of this material is thus strongly robust to lattice relaxations.

show abstract

“…It is found that the presence of LSWs can lead to rich conductance features even in the single particle transport regime. It is argued that transport energy gaps in the meV regime are not caused by an electronic instability due to electronic interactions as typically assumed [39; 40], but simply due to the structure of transport across LSWs and, in particular, due to "hot" charge carrying LSWs [41]. A similar argument for the presence of plateaus at fractional fillings [42][43][44] in BLG is made in [45], where arbitrary fractional plateaus are engineered in artificial SLG mosaics interconnected with metallic strips.…”

Section: Introductionmentioning

confidence: 99%

Effects of domain walls in bilayer graphene in an external magnetic field

Bassler,

Schmidt

2020

Preprint

View full text Add to dashboard Cite

We investigate bilayer graphene systems with layer switching domain walls separating the two energetically equivalent Bernal stackings in the presence of an external magnetic field. To this end we calculate quantum transport and local densities of three microscopic models for a single domain wall: a hard wall, a defect due to shear, and a defect due to tension. The quantum transport calculations are performed with a recursive Green's function method. Technically, we discuss an explicit algorithm for the separation of a system into subsystems for the recursion and we present an optimization of the well known iteration scheme for lead self-energies for sparse chain couplings. We find strong physical differences for the three different types of domain walls in the integer quantum Hall regime. For a domain wall due to shearing of the upper graphene layer there is a plateau formation in the magnetoconductance for sufficiently wide defect regions. For wide domain walls due to tension in the upper graphene layer there is only an approximate plateau formation with fluctuations of the order of the elementary conuctance quantum σ0. A direct transition between stacking regions like for the hard wall domain wall shows no plateau formation and is therefore not a good model for either of the previously mentioned extended domain walls.

show abstract

Dislocation and node states in bilayer graphene systems

Cited by 8 publications

References 17 publications

Perfect and Controllable Nesting in Minimally Twisted Bilayer Graphene

Perfect and Controllable Nesting in Minimally Twisted Bilayer Graphene

A general relation between stacking order and Chern index: a topological map of minimally twisted bilayer graphene

Effects of domain walls in bilayer graphene in an external magnetic field

Contact Info

Product

Resources

About