Magnetic proximity effect and electric-field modulation in Graphene-CrBr 3 van der Waals heterostructure Sushant Kumar Behera † , Mayuri Bora † , Sapta Sindhu Paul Chowdhury, Pritam Deb * Department of Physics, Tezpur University (Central University), Tezpur-784028, India. (Dated: May 13, 2022) We systematically explore the electronic and transport properties of Graphene-CrBr3 heterolayer based on ab initio density functional theory simulations. Our result shows the modulation in electronic band gap with applied electric field variation from -0.5 to +0.5 V/ ˚ A. The electric field variation marked linear and non-linear trend for band gap modulation due to polarization effects between the two layers. It is found that the transmission at the interface is spin polarized upto 71.2% and the magnetic moment is found to be invariant. Moreover, complex band structure and transmission spectrum reveals the possibilities of spin-transmission in Graphene-CrBr3 heterostructure via magnetic proximity effect. The merits of electric field tunability and magnetic proximity effect in this 2D layered ferromagnetic semiconductor heterostructure will be beneficial to extend its suitability in spintronics device applications. Magnetic proximity effect [1] is one of the most essential interfacial phenomena which gives an idea to model 2D magnetic heterostructure. Generally, proximity effects refer to the induction of an ordered state of magnetism in one layer that has an impact on another layer [2, 3]. When two different materials are brought into close vicinity, the impact of proximity effect results in the improvement of their properties and leading to variation of interfacial exchange coupling across the interface [4]. Recently, magnetic proximity effect has been studied via exchange coupling between non-magnet and magnetic substrates [5], non-magnetic bilayer systems [6]. In these cases, it is a challenging task to establish long-range magnetic ordering [7] and the magnetic moment induced from the substrate via proximity effect in non-magnetic material has limited effect in charge and spin-based transport properties [8]. Therefore, proximitized heterostructures in quantum regime exhibit novel properties superior than any con- stituents which remains an open area to overcome the limitations in spin-based device applications. Along with magnetic proximity effect, the van der Waals (vdW) heterostructures are quite flexible with incorporation of extrinsic perturbation like strain [9], electric-field [10, 11] magnetic-field [12] for its feasibility in device engineering. Graphene based heterostruc- tures have been explored in transistor applications [13] via effective gate tuning [14] and ballistic transport in ambient condition [15]. The electronic structure properties can be controlled via external effects in vdW heterostructure system [16]. In graphene-Cobalt based heterosystems, the electric field is altered between -0.1 V/ ˚ A and 0.1 V/ ˚ A [14]. Robust exchange interaction has been demonstrated theoretically where valley splitting is observed upto 70 meV in graphene-Bismuth Ferrite * Corresponding Author: pdeb@tezu.ernet.in(Pritam Deb); †These two authors contributed equally to this work. (BFO) heterostructure [17, 18]. Hybrid heterostructures like graphene-yttrium iron garnet (YIG) [19], graphene- EuO [18], graphene-hBN [13] have been studied for realizing anomalous Hall Effect [18] and topological phases [13]. Bringing atomically thin two-dimensional van der Waals materials in close proximity with unique interfa- cial behaviour is strategically an efficient approach to tailor the functionality of the materials. Graphene is considered as one of the model systems for nanospin- tronics applications for its suitability in high electron mobility and long spin relaxation length [20]. However, its possibilities are limited in spintronics due to the absence of magnetic ordering and its weak spin-orbit coupling. The limitation in graphene has triggered efforts to extrinsically induce local magnetic moments via various methods like doping or introducing magnetic material [21], induce defect engineering [22], or by introducing a magnetic substrate on which graphene layer is stacked [23]. Graphene layer with magnetic substrate is promising but, it has limitations in estab- lishing strong magnetic ordering and intrinsic moment induced from the substrate [7]. These limitations have enabled exploring possibilities on other two-dimensional crystals such as Chromium trihalides with intrinsic magnetic moment and a band gap ranges (1-2.6 eV) [9, 24]. The 2D ferromagnetic semiconductor combined with graphene to form magnetic heterostructure may have superiority in proximity as well as electric field modulations which are generally used as perturbative effect to vary the electronic property of the 2D het- erolayer system. van der Waals heterostructures like graphene-EuS [25], MoS 2 -EuS [26], graphene on h-BN induced by ferromagnets Co and Ni [27] has been studied for spin-valves and valley-splitting. In this letter, we opted for an ab initio density func- tional theory (DFT) study on Graphene-CrBr 3 (Gr- CrBr 3 ) heterostructure. Here, we focus on tuning band arXiv:1907.00866v1 [cond-mat.mes-hall] 1 Jul 2019