Transition metal dichalcogenides are known for their intriguing spin-valley effects, which can be harnessed through proximity in van der Waals heterostructures. Their hexagonal monolayers exhibit significant Zeeman band splitting of valence bands, reaching up to several hundred meV and giving rise to spin textures that yield long spin lifetimes. However, this effect is suppressed in the hexagonal bilayers due to inversion symmetry. The recent discovery of sliding ferroelectricity in ${MX}_2$ bilayers ($M=\mathrm{Mo}$, W; $X=\mathrm{S}$, Se) opens a pathway for the electrical control of the spin properties in these materials. While substantial Zeeman splitting is found in the rhombohedral structure, its behavior during the ferroelectric transition remains unclear. In this paper, we explore different stacking configurations of ${MX}_2$ bilayers by sliding and demonstrate, using density functional theory calculations and symmetry analysis, that the Zeeman effect completely dominates the spin polarization of bands throughout the structural transition. This promises to maintain robust spin transport in polar ${MX}_2$ bilayers, opening potential avenues for ferroelectric spintronics.

中文翻译：

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滑动铁电体中鲁棒的塞曼型能带分裂

过渡金属二硫属化物以其有趣的自旋谷效应而闻名，这种效应可以通过范德华异质结构中的接近来利用。它们的六边形单层表现出显着的价带塞曼带分裂，达到数百meV，并产生自旋纹理，从而产生长自旋寿命。然而，由于反演对称性，这种效应在六方双层中被抑制。最新发现的滑动铁电体${\mathrm{中号}X}_2$双层（$\mathrm{中号}=莫$，W；$X=\mathrm{S}$，Se）为这些材料中自旋特性的电控制开辟了途径。虽然在菱面体结构中发现了大量的塞曼分裂，但其在铁电转变期间的行为仍不清楚。在本文中，我们探索了不同的堆叠配置${\mathrm{中号}X}_2$通过滑动来实现双层结构，并使用密度泛函理论计算和对称性分析证明，塞曼效应完全主导了整个结构转变过程中能带的自旋极化。这有望在极地保持强大的自旋传输${\mathrm{中号}X}_2$双层，为铁电自旋电子学开辟了潜在途径。