论文标题
石墨烯对过渡金属磷硫酸盐的单层的接近效应MPX $ _3 $
Proximity effects in graphene on monolayers of transition-metal phosphorus trichalcogenides MPX$_3$
论文作者
论文摘要
我们在一系列二维磁过渡金属磷元素元素单层上研究石墨烯的电子带结构，M = {Mn，Fe，Fe，Ni，Co}和X = {S，SE，S，S，SE}，MPX $ _3 $，并进行了第一principles的计算。采用一种基于对称的模型哈密顿式的模型来提取轨道参数和转基因分析的接近诱导的交换耦合（$λ_{\ textrm {extrm {ex}}^\ textrm {a} $ {a} $ {a} $和$λ_邻近的石墨烯。根据MPX $ _3 $层的磁相（铁磁和三个反铁磁层），可以通过持续分布范围为0到10〜MEV，可以实现完全不同的Dirac分散体。令人惊讶的是，不仅交换耦合的大小取决于磁相，还取决于全局符号和类型。重要的是，人们可以实现统一（$λ_ {\ textrm {ex}}}^\ textrm {a} \ofλ_{\ textrm {ex}}}}^\ textrm {b} $ - λ_ {\ textrm {ex}}}^\ textrm {b} $）在石墨烯中交换耦合。从选定的情况下，我们发现层间距离以及横向电场是用于狄拉克带的交换分组的有效调整旋钮。更具体地说，仅将层间距离降低约10 \％，发现近距离交换的5倍增强，而在施加少量V/NM电场的同时，将接近交换的可调性降低了数百分之一。我们还研究了对Hubbard $ u $参数的依赖性，并发现它很弱。此外，我们发现与交换耦合相比，SOC对接近零的分散体的影响可以忽略不计。
We investigate the electronic band structure of graphene on a series of two-dimensional magnetic transition-metal phosphorus trichalcogenide monolayers, MPX$_3$ with M={Mn,Fe,Ni,Co} and X={S,Se}, with first-principles calculations. A symmetry-based model Hamiltonian is employed to extract orbital parameters and sublattice resolved proximity-induced exchange couplings ($λ_{\textrm{ex}}^\textrm{A}$ and $λ_{\textrm{ex}}^\textrm{B}$) from the low-energy Dirac bands of the proximitized graphene. Depending on the magnetic phase of the MPX$_3$ layer (ferromagnetic and three antiferromagnetic ones), completely different Dirac dispersions can be realized with exchange splittings ranging from 0 to 10~meV. Surprisingly, not only the magnitude of the exchange couplings depends on the magnetic phase, but also the global sign and the type. Important, one can realize uniform ($λ_{\textrm{ex}}^\textrm{A} \approx λ_{\textrm{ex}}^\textrm{B}$) and staggered ($λ_{\textrm{ex}}^\textrm{A} \approx -λ_{\textrm{ex}}^\textrm{B}$) exchange couplings in graphene. From selected cases, we find that the interlayer distance, as well as a transverse electric field are efficient tuning knobs for the exchange splittings of the Dirac bands. More specifically, decreasing the interlayer distance by only about 10\%, a giant 5-fold enhancement of proximity exchange is found, while applying few V/nm of electric field, provides tunability of proximity exchange by tens of percent. We have also studied the dependence on the Hubbard $U$ parameter and find it to be weak. Moreover, we find that the effect of SOC on the proximitized Dirac dispersion is negligible compared to the exchange coupling.
