Electrically tunable exchange splitting in bilayer graphene on monolayer Cr₂X₂Te₆ with X = Ge, Si, and Sn

Abstract

We investigate the electronic band structure and the proximity exchange effect in bilayer graphene (BLG) on a family of ferromagnetic multilayers Cr 2 X 2 Te 6 , X=Ge, Si, and Sn, with first principles methods. In each case the intrinsic electric field of the heterostructure induces an orbital gap on the order of 10 meV in the graphene bilayer. The proximity exchange is strongly band-dependent. For example, in the case of Cr 2 Ge 2 Te 6 , the low energy valence band of BLG has exchange splitting of 8 meV, while the low energy conduction band's splitting is 30 times less (0.3 meV). This striking discrepancy stems from the layer-dependent hybridization with the ferromagnetic substrate. Remarkably, applying a vertical electric field of a few V nm -1 reverses the exchange, allowing us to effectively turn ON and OFF proximity magnetism in BLG. Such a field-effect should be generic for van der Waals bilayers on ferromagnetic insulators, opening new possibilities for spin-based devices.

Chiral Majorana fermions in graphene from proximity-induced superconductivity

“…Graphene on transition-metal dichalcogenides (TMDCs) allows for staggered intrinsic SOC [17,[22][23][24][25][26][27][28][29][30], whereas on a topological insulator the intrinsic SOC in graphene can be uniform [31]. Similarly, the induced exchange coupling can be uniform [32][33][34][35][36][37][38][39][40][41][42][43] or staggered, as recently proposed [19]. In this part we fix the superconducting pairing to be equal on A and B, A S = B S = S = 0.03t, and use generic model parameters = 0.1t, λ R = 0.075t, λ A E = |λ B E | = 0.25t, and λ A I = |λ B I | = 3 √ 3 × 0.06t, if not indicated otherwise, to illustrate our findings.…”

Heterostructures of Graphene and Topological Insulators Bi2Se3, Bi2Te3, and Sb2Te3

“…[ 13 ] Within van der Waals heterostructures [ 14–16 ] with other 2D materials, one can induce magnetism, as well as strong spin‐orbit coupling (SOC) in graphene. [ 17–20 ] Combining proximity‐induced exchange and SOC in graphene can, under the right conditions, also lead to topologically protected edge states, [ 21,22 ] which could be important for novel spintronics applications.…”

Magnetic Entropy Scaling in Ferromagnetic Semiconductor CrGeTe3

“…Moreover, the 2D‐layered nature of CrXTe 3 make it a nice platform for the realization of functional van der Waals (vdW) heterostructures with other 2D materials. For example, it was predicted that graphene/CrGeTe 3 heterostructure introduces exchange splitting of graphene, leading to novel topological properties . Since the layered van der Waals (vdW) magnetic materials may also exhibit application in the magnetic refrigeration, in this work, we did the detailed research on the magnetocaloric effect and magnetic entropy scaling in CrGeTe 3 .…”

“…For example, it was predicted that graphene/CrGeTe 3 heterostructure introduces exchange splitting of graphene, leading to novel topological properties. [10,11] Since the layered van der Waals (vdW) magnetic materials may also exhibit application in the magnetic refrigeration, [12] in this work, we did the detailed research on the magnetocaloric effect and magnetic entropy scaling in CrGeTe 3 . The magnetic entropy and relative cooling power (RCP) are about 3.21 J kg À1 K À1 and 94.3 J kg À1 under applied magnetic field H ¼ 4.5 T, respectively.…”