Twisted Bilayer Graphene: Interlayer Configuration and Magnetotransport Signatures

Abstract

Twisted Bilayer Graphene may be viewed as very first representative of the now booming class of artificially layered 2D materials. Consisting of two sheets from the same structure and atomic composition, its decisive degree of freedom lies in the rotation between crystallographic axes in the individual graphene monolayers. Geometrical consideration finds angle-dependent Moiré patterns as well as commensurate superlattices of opposite sublattice exchange symmetry. Beyond the approach of rigidly interposed lattices, this review takes focus on the evolving topic of lattice corrugation and distortion in response to spatially varying lattice registry. The experimental approach to twisted bilayers requires a basic control over preparation techniques; important methods are summarized and extended on in the case of bilayers folded from monolayer graphene via AFM nanomachining. Central morphological parameters to the twisted bilayer, rotational mismatch and interlayer separation are studied in a broader base of samples. Finally, experimental evidence for a number of theoretically predicted, controversial electronic scenarios are reviewed; magnetotransport signatures are discussed in terms of Fermi velocity, van Hove singularities and Berry phase and assessed with respect to the underlying experimental conditions, thereby referring back to the initially considered variations in relaxed lattice structure.

Tuning the Interlayer Interaction of a Twisted Multilayer Wrinkle With Temperature

“…The FWHM of the thin wrinkles is much smaller than the FWHM of the thick wrinkles and is significantly overestimated by the AFM due to the convolution between the finite size AFM tip (typical FWHM of AFM probe is between 15 and 25 nm) and the narrow wrinkle. The real FWHM of a standing twisted wrinkle is expected to be below 1 nm to be able to observe the effects associated with a twisted bilayer. We also note that the wrinkle dimensions are well aligned with the previous reports, where the thin collapsed standing wrinkles can reach a maximum height of approximately 8 nm, after which they fold forming structures with various widths and complicated topography …”

High-TC Superconductivity Originating from Interlayer Coulomb Coupling in Gate-Charged Twisted Bilayer Graphene Moiré Superlattices

“…Modeling the form of ∆z as sinusoidal modulations of wavelength λ m with the 6-fold symmetry of a triangular lattice [62,63] yields the result ζ = z AA + f z (z AA − z AB ) with f z = 1/1.8.…”

Time-evolution patterns of electrons in twisted bilayer graphene

“…5,11,13,14 In particular, the lattice alignment is commensurate only when the twist angle takes the values given by the formula θ = acos[(3m 2 + 3mr + r 2 /2)/(3m 2 + 3mr + r 2 )], in which m, r are positive coprime integers. 5,11,[13][14][15][16] When the stacking is commensurate, the translational symmetry of the TBG lattice is preserved, but it usually defines a large unit cell, especially for small twist angles θ. The electronic calculation for such TBG configurations by brute force diagonalization is therefore extremely expensive in terms of computational resources.…”