Straintronics beyond homogeneous deformation

Gupta, R.; Rost, F.; Fleischmann, M.; Sharma, S.; Shallcross, S.

doi:10.1103/physrevb.99.125407

Cited by 17 publications

(33 citation statements)

References 71 publications

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“…with σ = (σ x , σ y ) the vector of Pauli matrices and σ 0 the identity matrix. The mapping process generates also optical deformation terms 28 , which turn out to be zero for the relaxation field of the twist bilayer, as well as higher order terms in momentum and derivatives and powers of the deformation tensor. The interlayer coupling of these single layer blocks is given in the continuum representation by…”

Section: B Electronic Hamiltonianmentioning

confidence: 99%

Perfect and Controllable Nesting in Minimally Twisted Bilayer Graphene

et al. 2019

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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...

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Section: B Electronic Hamiltonianmentioning

confidence: 99%

Perfect and Controllable Nesting in Minimally Twisted Bilayer Graphene

et al. 2019

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“…In the following discussion, we use the short name (n-m) to describe the structure of the SL of LaCoO 3 with the thickness of n unit cells and SrTiO 3 with m unit cells. (Figure 1a) shows the representative RHEED oscillations for SL (5-3) and (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15), respectively. It is seen that both LaCoO 3 and SrTiO 3 show well-defined oscillation patterns throughout the entire film growth procedure, demonstrating layer-by-layer growth mode for both layers.…”

Section: Resultsmentioning

confidence: 99%

“…This is the famous quotation from Prof. Herbert Kroemer for 2000 Nobel Prize in Physics, which illustrates the successful achievements for advanced electronics based on classic semiconductor heterostructures since 1960s. [1] The concept of interface being the device [2] still holds true even for recent scientific and technological breakthroughs in valleytronics, [3] twistronics, [4,5] spintronics, [6,7] orbitronics, [8] and straintronics [9,10] that use transition-metal based compounds. Among these materials, heterostructures formed by transitionmetal complex oxides with perovskite crystal structure have attracted significant attention due to the emergent interfacial physics and materials properties.…”

Section: Introductionmentioning

confidence: 99%

Crystal Symmetry Engineering in Epitaxial Perovskite Superlattices

Ding

Yang

Leng

et al. 2021

Adv Funct Materials

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Interface plays a critical role in determining the physical properties and device performance of heterostructures. Traditionally, lattice mismatch, resulting from the different lattice constants of the heterostructure, can induce epitaxial strain. Over past decades, strain engineering has been demonstrated as a useful strategy to manipulate the functionalities of the interface. However, mismatch of crystal symmetry at the interface is relatively less studied due to the difficulty of atomically structural characterization, particularly for the epitaxy of low symmetry correlated materials on the high symmetry substrates. Overlooking those phenomena restrict the understanding of the intrinsic properties of the as‐ determined heterostructure, resulting in some long‐standing debates including the origin of magnetic and ferroelectric dead layers. Here, perovskite LaCoO3‐SrTiO3 superlattice (SL) is used as a model system to show that the crystal symmetry effect can be isolated by the existing interface strain. Combining the state‐of‐art diffraction and electron microscopy, it is found that the symmetry mismatch of LaCoO3‐SrTiO3 SL can be tuned by manipulating the SrTiO3 layer thickness to artificially control the magnetic properties. The work suggests that crystal symmetry mismatch can also be designed and engineered to act as an effective strategy to generate functional properties of perovskite oxides.

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“…The impact of such in-plane deformation upon the electronic structure of partial dislocations has been explored in Ref. 11 and found to be negligible, and so we do not consider the resulting gauge, scalar, and Fermi velocity correction terms in the layer-diagonal blocks of our effective Hamiltonian 18 .…”

Section: A Continuum Description Of a Partial Networkmentioning

confidence: 99%

Dislocation and node states in bilayer graphene systems

et al. 2019

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We investigate the electronic structure of realistic partial dislocation networks in bilayer graphene that feature annihilating, wandering, and intersecting partial lines. We find charge accumulation states at partials that are sensitive to Fermi energy and partial Burgers vector but not to the screw versus edge character of the partial. These states are shown to be current carrying, with the current density executing a spiral motion along the dislocation line with a strong interlayer component to the current. Close to the Dirac point localization on partials switches to localization on intersections of partials, with a corresponding complex current flow around the nodes.

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Straintronics beyond homogeneous deformation

Cited by 17 publications

References 71 publications

Perfect and Controllable Nesting in Minimally Twisted Bilayer Graphene

Perfect and Controllable Nesting in Minimally Twisted Bilayer Graphene

Crystal Symmetry Engineering in Epitaxial Perovskite Superlattices

Dislocation and node states in bilayer graphene systems

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