AI 中文总结
本文研究了范德华磁性隧道结中界面态与应变对隧道磁阻的影响，揭示了势垒厚度、双轴拉伸应变可调控TMR比率，为增强全二维磁性隧道结的TMR效应提供了有效途径。
AI 中文摘要
全二维磁性隧道结有望实现原子级尖锐界面，但界面诱导态在其自旋输运中的作用尚未完全明确。本文从理论上研究了结构为Cr₂C/MY₂/Cr₂C（M=Mo、W；Y=S、Se）、势垒厚度为3、5、7、9层的范德华磁性隧道结中的自旋依赖输运。k∥分辨电导的主要特征——Γ点附近的抑制与六个非Γ热点处的增强，与势垒中倏逝态的衰减一致。然而，三层WS₂、MoSe₂和WSe₂势垒在热点内的k∥点处呈现出量级为e²/h的电导，我们将这些近单位透射通道归因于两个电极-势垒界面处界面态之间的共振耦合，这一点由其在势垒中心处存在弱但有限的残余权重所证实。对于更厚的势垒，这种耦合会减弱，从而抑制残余权重，进而降低MoS₂结的隧道磁阻（TMR）比率，同时提高其他结的TMR比率。为利用界面态实现自旋选择隧穿，我们进一步研究了施加在三层势垒上的双轴拉伸应变。在4%应变下，MoS₂的TMR比率从176%提升至540%，WS₂的TMR比率从98%提升至496%，而MoSe₂和WSe₂的提升则相对较弱。我们的结果表明，通过应变和势垒厚度进行界面态工程是增强全二维磁性隧道结中TMR效应的有效途径。
英文摘要
All-two-dimensional magnetic tunnel junctions promise atomically sharp interfaces, yet the role of interface-induced states in their spin transport is not fully understood. Here, we theoretically investigate spin-dependent transport in van der Waals magnetic tunnel junctions of the structure Cr$_2$C/$MY_2$/Cr$_2$C ($M$ = Mo, W; $Y$ = S, Se) with barrier thicknesses of 3, 5, 7, and 9 layers. The broad features of the $\mathbf{k}_{\parallel}$-resolved conductances, namely suppression near the $Γ$ point and enhancement at six off-$Γ$ hot spots, are consistent with the decay of evanescent states in the barrier. However, trilayer WS$_2$, MoSe$_2$, and WSe$_2$ barriers exhibit conductances of the order of $e^2/h$ at $\mathbf{k}_{\parallel}$ points within the hot spots. We attribute these near-unity transmission channels to resonant coupling between the interfacial states at the two electrode--barrier interfaces, as evidenced by their weak but finite residual weight at the barrier center. For thicker barriers, this coupling weakens, which suppresses the residual weight, thereby reducing the tunnel magnetoresistance (TMR) ratio of the MoS$_2$ junction while enhancing those of the other junctions. To exploit the interfacial states for spin-selective tunneling, we further examine biaxial tensile strain applied to the trilayer junctions. At 4\% strain, the TMR ratio increases from 176\% to 540\% for MoS$_2$ and from 98\% to 496\% for WS$_2$, whereas MoSe$_2$ and WSe$_2$ exhibit comparatively weaker enhancement. Our results establish interfacial-state engineering via strain and barrier thickness as effective routes for enhancing the TMR effect in all-two-dimensional magnetic tunnel junctions.
