Electric-Field-Tunable Valley Zeeman Effect in Bilayer Graphene Heterostructures: Realization of the Spin-Orbit Valve Effect

Tiwari, Priya; Bid, Aveek

doi:10.1103/physrevlett.126.096801

Cited by 32 publications

(35 citation statements)

References 34 publications

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“…Also proximity effects can induce spin interactions in BLG. As theoretically predicted by first-principles calculations [30] and recently confirmed via penetration field * klaus.zollner@physik.uni-regensburg.de capacitance measurements [35] and mesoscopic transport [37], a transition-metal dichalcogenide (TMDC) in proximity to BLG strongly enhances the SOC of the adjacent graphene layer only. By applying a gate voltage, one can then fully electrically turn on and off the SOC of the BLG conduction electrons.…”

Section: Introductionmentioning

confidence: 62%

“…In this context, bilayer graphene (BLG) has emerged as a model playground for gate-and twist-tunable correlated physics [23][24][25][26][27][28][29] as well as for layer-dependent proximity-induced spin interactions [10,[30][31][32][33][34][35][36][37]. Two sheets of graphene stacked at a small twist angle can become insulating, ferromagnetic [28], or superconducting [23][24][25][26][27] under certain filling factors of the Moiré Brillouin zone.…”

Section: Introductionmentioning

confidence: 99%

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Bilayer graphene encapsulated within monolayers of WS2 or Cr2Ge2Te6 : Tunable proximity spin-orbit or exchange coupling

Zollner

Fabian

2021

Phys. Rev. B

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Van der Waals (vdW) heterostructures consisting of bilayer graphene (BLG) encapsulated within monolayers of strong spin-orbit semiconductor WS2 or ferromagnetic semiconductor Cr2Ge2Te6 (CGT), are investigated. By performing realistic first-principles calculations we capture the essential BLG band structure features, including layer-and sublattice-resolved proximity spin-orbit or exchange couplings. For different relative twist angles (0 or 60 • ) of the WS2 layers, and the magnetizations (parallel or antiparallel) of the CGT layers, with respect to BLG, the low energy bands are found and characterized by a series of fit parameters of model Hamilatonians. These effective models are then employed to investigate the tunability of the relevant energy dispersions by a gate field. For WS2/BLG/WS2 encapsulation we find that twisting allows to turn off the spin splittings away from the K points, due to opposite proximity-induced valley-Zeeman couplings in the two sheets of BLG. Close to the K points the electron spins are polarized out of the plane. This polarization can be flipped by applying a gate field. As for magnetic CGT/BLG/CGT structures, we realize the recently proposed spin-valve effect, whereby a gap opens for antiparallel magnetizations of the CGT layers. Furthermore, we find that for the antiferromagnetic orientation the electron states away from K have vanishingly weak proximity exchange, while the states close to K remain spin polarized in the presence of an electric field. The induced magnetization can be flipped by changing the gate field. These findings should be useful for spin transport, spin filtering, and spin relaxation anisotropy studies of BLG-based vdW heterostructures.

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Section: Introductionmentioning

confidence: 62%

Section: Introductionmentioning

confidence: 99%

Bilayer graphene encapsulated within monolayers of WS2 or Cr2Ge2Te6 : Tunable proximity spin-orbit or exchange coupling

Zollner

Fabian

2021

Phys. Rev. B

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“…Recent experiments studied related structures in the context of gate-defined TBG Josephson junctions [20,21]. In our case, the TMD substrate serves to impart appreciable spinorbit coupling (SOC)-which plays a pivotal role throughout this paper-to the graphene sheets, as seen in many experiments [12,[22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Notably, Ref.…”

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confidence: 91%

Gate-defined wires in twisted bilayer graphene: From electrical detection of intervalley coherence to internally engineered Majorana modes

et al. 2022

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Twisted bilayer graphene (TBG) realizes a highly tunable, strongly interacting system featuring superconductivity and various correlated insulating states. We establish gate-defined wires in TBG with proximity-induced spin-orbit coupling as (i) a tool for revealing the nature of correlated insulators and (ii) a platform for Majoranabased topological qubits. In particular, we show that the band structure of a gate-defined wire immersed in an 'inter-valley coherent' correlated insulator inherits electrically detectable fingerprints of symmetry breaking native to the latter. Surrounding the wire by a superconducting TBG region on one side and an inter-valley coherent correlated insulator on the other further enables the formation of Majorana zero modes-possibly even at zero magnetic field depending on the precise symmetry-breaking order present. Our proposal not only introduces a highly gate-tunable topological qubit medium relying on internally generated proximity effects, but can also shed light on the Cooper-pairing mechanism in TBG.

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“…In addition, the vertically assembled heterostructure of graphene with TMDs has a proclivity to modify the interfacial interaction such that the SOI in graphene is enhanced [20,21]. Taking advantage of the proximity effect in stacked 2D materials, one can impart desirable properties on graphene without disturbing the genuine characteristics [22][23][24][25][26][27]. Recently, in our previous study [28], the WS 2 /bilayer graphene (BLG)/WS 2 heterostructure exhibited a noticeable phenomenon of weak anti-localization (WAL) and zero-field spin splitting due to a strong SOI.…”

Section: Introductionmentioning

confidence: 99%

Gate-Voltage-Modulated Spin Precession in Graphene/WS2 Field-Effect Transistors

2021

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Transition metal dichalcogenide materials are studied to investigate unexplored research avenues, such as spin transport behavior in 2-dimensional materials due to their strong spin-orbital interaction (SOI) and the proximity effect in van der Waals (vdW) heterostructures. Interfacial interactions between bilayer graphene (BLG) and multilayer tungsten disulfide (ML-WS2) give rise to fascinating properties for the realization of advanced spintronic devices. In this study, a BLG/ML-WS2 vdW heterostructure spin field-effect transistor (FET) was fabricated to demonstrate the gate modulation of Rashba-type SOI and spin precession angle. The gate modulation of Rashba-type SOI and spin precession has been confirmed using the Hanle measurement. The change in spin precession angle agrees well with the local and non-local signals of the BLG/ML-WS2 spin FET. The operation of a spin FET in the absence of a magnetic field at room temperature is successfully demonstrated.

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Electric-Field-Tunable Valley Zeeman Effect in Bilayer Graphene Heterostructures: Realization of the Spin-Orbit Valve Effect

Cited by 32 publications

References 34 publications

Bilayer graphene encapsulated within monolayers of WS2 or Cr2Ge2Te6 : Tunable proximity spin-orbit or exchange coupling

Bilayer graphene encapsulated within monolayers of WS2 or Cr2Ge2Te6 : Tunable proximity spin-orbit or exchange coupling

Gate-defined wires in twisted bilayer graphene: From electrical detection of intervalley coherence to internally engineered Majorana modes

Gate-Voltage-Modulated Spin Precession in Graphene/WS2 Field-Effect Transistors

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