Study On Transport Properties Of Van Der Waals Heterojunction Based On Gr|2ML-CrI₃(AB)|Gr

The spin and charge are inherent natures of electron.The former is mainly used as the information processing and transmission,the latter is always employed to the information storage.If one material have both the two attributes,it will be suitable for spintronic devices.Spin valves and magnetic tunneling junctions(MTJs),are a crucial component to spintronic devices.MTJs have the most extensive application.Previous investigations has shown that MTJs have perfect spin filtering effect and high tunnel magnetoresistance(TMR),which play an essential part in upgrading spin injection efficiency and magnetic information storage.TMR is an important physical phenomenon that has a tremendous impact on magnetic information storage.However,MTJs are increasingly unable to satisfy the pressing demand of the modern society.For example,traditional MTJs are confronted with many issues in terms of the defect and disorder present in the electrodes,barrier,electrode-barrier interface,oxided-interface in heterojunctions,low device lifetime and damanable thermal stability,leading to a low TMR ratio.With the rapid development of two-dimensional materials,a host of two-dimensional intrinstic magnetic materials have been discovered successively.Subsequently,van der Waals heterostructures based on diverse two-dimensional materials have become a priority field of MTJs.Accordingly,first-rate two-dimensional materials with high Cuire temperature,realtively high carrier mobility,nearly 100%spin-polarization percentage and large perpendicular anisotropy are badly demanded.Gr and CrI₃are the brightest stars among two-dimensional materials depending on their prominent features.Inspired by above-mentioned,combing Gr with bilayer CrI₃,a van der Waals heterojunction,can mutually draw on each other's strong points and overcome their own weaknesses.Here,we employ the first-principles calculation method to probe the interfacial structure and band structure of Gr|CrI₃ heterojunction.Moreover,we adopt density functional theory combined with nonequibrium Green's function(NEGF-DFT)to study the quantum transport properties of Gr|2ML-CrI₃(AB)|Gr,which exhibits a series of excellent features,such as 100%spin injection efficiency and high magnetic tunneling resistance,which provide a theortical support for designing van der waals devices.The major substance and results are concentrated into the following three viewpoints:1.We design a new-type Gr|2ML-CrI₃(AB)|Gr heterojunction and pursue intensive research on the interfacial structure and van der Waals gap of Gr|2ML-CrI₃(AB)|Gr heterojunction.There are nearly no difference in terms of vd W gap and relaxed energy among six kinds of interfacial structure,in other words,interfacial structure exerts little influence on stability and magnetism of Gr|2ML-CrI₃(AB)|Gr heterojunction.2.We analyze band structures of Gr|2ML-CrI₃(AB)|Gr heterostructure with ferromagnetic(FM)(PC)and antiferromagnetic(AFM)(APC)ordering between CrI₃ layers,respectively.In FM state,for spin-up electrons,they can soundly pass through the barrier,for spin-down electrons,they encounter a wide gap,so can't smoothly go through the barrier.In AFM state,both spin-up and–down electrons encounter a gap and can't smoothly go through the barrier layer.However,there are minor spin-up and–down electrons due to dispersions of some occupied Dirac states.3.We study the quantum transport properties on the system by NEGF-DFT.Our results uncover that Gr|2ML-CrI₃(AB)|Gr has a perfect spin filtering effect.For the PC,the spin-polarization percentage can reach 100%,filtering all spin-down electrons.For the APC,the spin-polarization percentage is less than 50%.The system has a giant TMR.It is worth noting that TMR has a maximum value of near 20000%under 0.05V.In addition,remarkable negative differential resistance(NDR)phenomenon occurs in some bias ranges.The findings supply a theoretical support for producing van der Waals MTJs in experiments.