Theory of proximity-induced exchange coupling in graphene on hBN/(Co, Ni)

Abstract

We perform systematic first-principles calculations of the proximity exchange coupling, induced by cobalt (Co) and nickel (Ni) in graphene, via a few (up to three) layers of hexagonal boron nitride (hBN). We find that the induced spin splitting of the graphene bands is of the order of 10 meV for a monolayer of hBN, decreasing in magnitude but alternating in sign by adding each new insulating layer. We find that the proximity exchange can be giant if there is a resonant $d$ level of the transition metal close to the Dirac point. Our calculations suggest that this effect could be present in Co heterostructures, in which a $d$ level strongly hybridizes with the valence-band orbitals of graphene. Since this hybridization is spin dependent, the proximity spin splitting is unusually large, about 10 meV even for two layers of hBN. An external electric field can change the offset of the graphene and transition-metal orbitals and can lead to a reversal of the sign of the exchange parameter. This we predict to happen for the case of two monolayers of hBN, enabling electrical control of proximity spin polarization (but also spin injection) in graphene/hBN/Co structures. Nickel-based heterostructures show weaker proximity effects than cobalt heterostructures. We introduce two phenomenological models to describe the first-principles data. The minimal model comprises the graphene (effective) $p_z$ orbitals and can be used to study transport in graphene with proximity exchange, while the $p_z$-$d$ model also includes hybridization with $d$ orbitals, which is important to capture the giant proximity exchange. Crucial to both models is the pseudospin-dependent exchange coupling, needed to describe the different spin splittings of the valence and conduction bands.

14 pages, 17 figures, 2 tables

References in corpus (22)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• The electronic properties of graphene
• Doping graphene with metal contacts
• Graphene Spintronics
• Magnetism in Graphene Induced by Single-Atom Defects
• Emergence of magnetism in graphene materials and nanostructures
• Atomic-scale control of graphene magnetism using hydrogen atoms
• Proximity-induced ferromagnetism in graphene revealed by anomalous Hall effect
• Calculations of Hubbard U from first-principles
• Graphite and graphene as perfect spin filters
• Tunneling Spin Injection into Single Layer Graphene
• Tunneling Spin Injection into Single Layer Graphene (Supplementary Information)
• Quantum Anomalous Hall Effect in Graphene Proximity Coupled to an Antiferromagnetic Insulator
• Magnetic Insulator-Induced Proximity Effects in Graphene: Spin Filtering and Exchange Splitting Gaps
• Magnetic Moment Formation in Graphene Detected by Scattering of Pure Spin Currents
• Spin Injection into a Graphene Thin Film at Room Temperature
• Graphene-Passivated Nickel as an Oxidation-Resistant Electrode for Spintronics
• Spin-orbit coupling in fluorinated graphene
• Dynamic Spin Injection into Chemical Vapor Deposited Graphene
• Efficient spin injection into graphene through a tunnel barrier: overcoming the spin conductance mismatch
• Ab initio spin-flip conductance of hydrogenated graphene nanoribbons: Spin-orbit interaction and scattering with local impurity spins
• Field effect doping of graphene in metal|dielectric|graphene heterostructures: a model based upon first-principles calculations

Cited by in corpus (26)

• Van der Waals heterostructures for spintronics and opto-spintronics
• Electrical and Thermal Generation of Spin Currents by Magnetic Graphene
• Quantum Anomalous Hall Effects in Graphene from Proximity-Induced Uniform and Staggered Spin-Orbit and Exchange Coupling
• Twist- and gate-tunable proximity spin-orbit coupling, spin relaxation anisotropy, and charge-to-spin conversion in heterostructures of graphene and transition-metal dichalcogenides
• Giant proximity exchange and valley splitting in transition metal dichalcogenide/$h\mathrm{BN}$/(Co, Ni) heterostructures
• Spin caloritronics in a CrBr${}_3$-based magnetic van der Waals heterostructure
• Engineering Proximity Exchange by Twisting: Reversal of Ferromagnetic and Emergence of Antiferromagnetic Dirac Bands in Graphene/Cr${}_2$Ge${}_2$Te${}_6$
• Proximity effects in graphene on monolayers of transition-metal phosphorus trichalcogenides MPX${}_3$
• Bilayer graphene encapsulated within monolayers of WS${}_2$ or Cr${}_2$Ge${}_2$Te${}_6$: Tunable proximity spin-orbit or exchange coupling
• Proximity spin-orbit and exchange coupling in ABA and ABC trilayer graphene van der Waals heterostructures
• Emergent correlated phases in rhombohedral trilayer graphene induced by proximity spin-orbit and exchange coupling
• Spin-orbit and exchange proximity couplings in graphene/1T-TaS${}_2$ heterostructure triggered by a charge density wave
• Spin-selectable, region-tunable negative differential resistance in graphene double ferromagnetic barriers
• Topological edge states of a graphene zigzag nanoribbon with spontaneous edge magnetism
• Swapping exchange and spin-orbit induced correlated phases in proximitized Bernal bilayer graphene
• Electric-field-induced extremely large change in resistance in graphene ferromagnets
• Manipulating Spin-Lattice Coupling in Layered Magnetic Topological Insulator Heterostructure $via$ Interface Engineering
• Supercell Wannier functions and a faithful low-energy model for Bernal bilayer graphene
• Hydrostatic pressure control of the spin-orbit proximity effect, spin relaxation, and thermoelectricity in a phosphorene-WSe${}_2$ heterostructure
• Proximity-enabled control of spin-orbit coupling in phosphorene symmetrically and asymmetrically encapsulated by WSe${}_2$ monolayers
• Rashba spin-orbit coupling enhanced magnetoresistance in junctions with one ferromagnet
• Zigzag nanoribbon of gated bilayer hexagonal crystals with spontaneous edge magnetism
• Angular dependence of the interlayer coupling at the interface between two dimensional materials 1T-PtSe${}_2$ and graphene
• First-order effect of electron-electron interactions on the anomalous Hall conductivity of massive Dirac fermions
• Electronic and Spin-Orbit Properties of hBN Encapsulated Bilayer Graphene
• Moiré Folded Helical States at the Interfaces of Heterostructures