层状极性Dirac金属中的可调谐自旋谷耦合
Tunable spin-valley coupling in layered polar Dirac metals
摘要：
在非中心对称的金属中，自旋轨道耦合（SOC）在费米表面诱导动量相关的自旋极化。这是例证谷对比自旋极化在单层过渡金属二硫属化物（TMDC）与面内反转不对称。然而，在TMDC中，大量狄拉克费米子的谷位形被石墨烯类结构固定，这限制了自旋谷耦合的多样性。在这里，我们表明，层状极性金属BaMn $X_2$（$X =$ Bi，Sb）主机可调自旋谷耦合狄拉克费米子，这源于扭曲的$X$方网与面内晶格极化。我们发现，尽管更大的SOC，BaMnBi $_2$有大约十分之一的晶格畸变的BaMnSb $_2$，从理论上预测的自旋极化狄拉克谷的不同配置。这在实验上被观察到为两种材料之间在高场下的Shubnikov-de Haas振荡中的明显差异。BaMn $X_2$的可调谐自旋谷耦合特性使其成为一种很有前途的自旋谷电子器件材料。
英文摘要：
In non-centrosymmetric metals, spin-orbit coupling (SOC) induces momentum-dependent spin polarization at the Fermi surfaces. This is exemplified by the valley-contrasting spin polarization in monolayer transition metal dichalcogenides (TMDCs) with in-plane inversion asymmetry. However, the valley configuration of massive Dirac fermions in TMDCs is fixed by the graphene-like structure, which limits the variety of spin-valley coupling. Here, we show that the layered polar metal BaMn$X_2$ ($X =$Bi, Sb) hosts tunable spin-valley-coupled Dirac fermions, which originate from the distorted $X$ square net with in-plane lattice polarization. We found that in spite of the larger SOC, BaMnBi$_2$ has approximately one-tenth the lattice distortion of BaMnSb$_2$, from which a different configuration of spin-polarized Dirac valleys is theoretically predicted. This was experimentally observed as a clear difference in the Shubnikov-de Haas oscillation at high fields between the two materials. The chemically tunable spin-valley coupling in BaMn$X_2$ makes it a promising material for various spin-valleytronic devices.
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