Tunable spin-polarized correlated states in twisted double bilayer graphene

Liu, Xiaomeng; Hao, Zeyu; Khalaf, Eslam; Lee, Jong Yeon; Ronen, Yuval; Yoo, Hyobin; Najafabadi, Danial Haei; Watanabe, Kenji; Taniguchi, Takashi; Vishwanath, Ashvin; Kim, Philip

doi:10.1038/s41586-020-2458-7

Cited by 563 publications

(471 citation statements)

References 36 publications

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“…2. Such resonant tunneling occurs since for θ 1 = θ 3 [hence, (1) v = (3) v ] evanescent modes corresponding to any energy (the entire blue region in Fig. 2) participate in tunneling.…”

Section: Array Of Dws: Resonant Tunnelingmentioning

confidence: 99%

“…are among the most innate tuning parameters which can fundamentally transform, thereby help us understand, many condensed matter systems. As a result of the discovery of correlated insulation [1] and superconductivity [2] in twisted bilayer graphene (TBG), a twist angle has been envisaged as a conspicuously novel control parameter that can allow various layered van der Waals materials to host myriads of intriguing phases [3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

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Transport across twist angle domains in moiré graphene

Padhi

Tiwari

Neupert

et al. 2020

Phys. Rev. Research

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Many experiments in twisted bilayer graphene (TBG) differ from each other in terms of the details of their phase diagrams. Few controllable aspects aside, this discrepancy is largely believed to arise from the presence of a varying degree of twist angle inhomogeneity across different samples. Real-space maps indeed reveal TBG devices splitting into several large domains of different twist angles. Motivated by these observations, we study the quantum mechanical tunneling across a domain wall (DW) that separates two such regions. We show that the tunneling of the moiré particles can be understood by the formation of an effective step potential at the DW. The height of this step potential is simply a measure of the difference in twist angles. These computations lead us to identify the global transport signatures for detecting and quantifying the local twist angle variations. In particular, using Landauer-Büttiker formalism, we compute single-channel conductance (dI/dV) and Fano factor for shot noise (ratio of noise power and mean current). A reduction in the low-energy conductance and a zero-bias sub-meV gap in the conductance are observed which scale with the twist angle difference. One of the key findings of our work is that transport in presence of twist angle inhomogeneity is "noisy," though sub-Poissonian. In particular, the differential Fano factor peaks near the van Hove energies corresponding to the domains in the sample. The location and the strength of the peak are simply a measure of the degree of twist angle inhomogeneity.

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“…2. Such resonant tunneling occurs since for θ 1 = θ 3 [hence, (1) v = (3) v ] evanescent modes corresponding to any energy (the entire blue region in Fig. 2) participate in tunneling.…”

Section: Array Of Dws: Resonant Tunnelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Transport across twist angle domains in moiré graphene

Padhi

Tiwari

Neupert

et al. 2020

Phys. Rev. Research

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“…One interesting possibility is the twisted doublebilayer. This four-layer system [28][29][30] has a relative twist between two untwisted bilayers, and it is expected to have flat bands whose properties depend on an even wider range of tunable variables compared with simple TBG. Another option is to place a graphene multilayer system on a hexagonal boron nitride substrate, which modifies the multilayer's properties [31,32].…”

Section: Beyond the Simple Bilayermentioning

confidence: 99%

Bilayer Graphene’s Wicked, Twisted Road

MacDonald

2019

Physics

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“…Besides TBG, twisted double bilayer graphene (TDBG) with relative rotation between the top and bottom graphene bilayers has been realized recently [28][29][30] . In addition to the nearly flat middle bands in TDBG with a small θ, a gap at E F is opened, and among various stacking arrangements between the bilayers AB-BA TDBG can become valley Hall insulators [31][32][33][34][35] .…”

Section: Introductionmentioning

confidence: 99%

Pressure-induced gap modulation and topological transitions in twisted bilayer and twisted double bilayer graphene

Lin

Zhu

2020

Phys. Rev. B

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We study the electronic and topological properties of fully relaxed twisted bilayer (TBG) and double bilayer (TDBG) graphene under perpendicular pressure. An approach has been proposed to obtain the equilibrium in-plane structural deformation and out-of-plane corrugation in moiré superlattices under pressure. We find that the in-plane relaxation becomes much stronger under higher pressure, while the corrugation height in each layer is maintained. The comparison between band structures of relaxed and rigid structures demonstrates that not only the gaps on the electron and hole sides (∆e and ∆ h) are significantly underestimated without relaxation but also the detailed dispersions of the middle bands of rigid structures are rather different from those of relaxed systems. ∆e and ∆ h in TBG reach maximum values around critical pressures with narrowest middle bands. Topological transitions occur in TDBG under pressure with the middle valence and conduction bands in one valley touching and their Chern numbers transferred to each other. The pressure can also tune the gap at the neutrality point of TDBG, which becomes closed for a pressure range and reopened under higher pressure. The behavior of electronic structure of supertlattices under pressure is sensitive to the twist angle θ with the critical pressures generally increase with θ.

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Tunable spin-polarized correlated states in twisted double bilayer graphene

Cited by 563 publications

References 36 publications

Transport across twist angle domains in moiré graphene

Transport across twist angle domains in moiré graphene

Bilayer Graphene’s Wicked, Twisted Road

Pressure-induced gap modulation and topological transitions in twisted bilayer and twisted double bilayer graphene

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