反铁磁单层Cr2S2中自旋-谷锁定和谷霍尔效应的分数量子铁电控制
Fractional quantum ferroelectric control of spin-valley locking and valley Hall effects in altermagnetic monolayer Cr2S2
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中文总结 AI 辅助
研究单层Cr2S2中自旋-谷锁定和谷霍尔效应的分数量子铁电控制。通过第一性原理计算，利用复合对称操作实现二维FQFE-AM平台及可切换状态，实现极化可切换的自旋-谷锁定和极化控制的谷霍尔效应，为低功耗谷电子器件提供途径。
中文摘要 AI 辅助
分数量子多铁性源于分数量子铁电（FQFE）与反铁磁（AM）之间的耦合，为净磁矩为零的系统中动量依赖的自旋分裂的非易失性控制提供了一个有前景的平台。然而，将这种FQFE-AM耦合扩展到谷自由度和贝里曲率驱动的谷霍尔效应在很大程度上仍未被探索。本文通过第一性原理计算表明，单层Cr2S2实现了二维FQFE-AM平台，具有两个可切换的FQFE状态，通过结合分数晶格平移与时间反演或宇称-时间反演的复合对称操作相连。我们表明，FQFE切换会反转AM自旋极化能带结构，并在不旋转奈尔矢量的情况下交换X和Y谷的自旋特征，从而实现极化可切换的自旋-谷锁定。此外，两个FQFE状态表现出相反的贝里曲率分布，这与切换后的自旋-谷锁定一起，在电子和空穴掺杂下都能实现极化控制的谷霍尔效应。这些结果证明了一种基于对称性的机制，用于对AM自旋分裂、自旋-谷锁定和谷霍尔效应进行非易失性电控制，为基于FQFE-AM耦合的低功耗谷电子器件提供了一条通用途径。
英文摘要
Fractional quantum multiferroics, arising from the coupling between fractional quantum ferroelectricity (FQFE) and altermagnetism (AM), provide a promising platform for nonvolatile control of momentum dependent spin splitting in systems with zero net magnetization. However, extending this FQFE-AM coupling to valley degrees of freedom and Berry curvature driven valley Hall effects remains largely unexplored. Here, using first-principles calculations, we demonstrate that monolayer Cr2S2 realizes a two dimensional FQFE-AM platform with two switchable FQFE states connected by composite symmetry operations combining a fractional lattice translation with time reversal or parity-time reversal. We show that FQFE switching reverses the AM spin-polarized band structure and interchanges the spin characters of the X and Y valleys without rotating the Néel vector, thereby enabling polarization switchable spin-valley locking. Moreover, the two FQFE states exhibit reversed Berry curvature distributions, which, together with the switched spin-valley locking, enable polarization controlled valley Hall effects under both electron and hole doping. These results demonstrate a symmetry based mechanism for nonvolatile electrical control of AM spin splitting, spin-valley locking, and valley Hall effects, offering a general route toward low-power valleytronic devices based on FQFE-AM coupling.
