论文标题
增强了Ql-XSBO $ _2 $（x = li，na）的增强的平面内铁电性，抗抗逆火和非常规2d的fermions
Enhanced in-plane ferroelectricity, antiferroelectricity, and unconventional 2D emergent fermions in QL-XSbO$_2$ (X= Li, Na)
论文作者
论文摘要
具有受保护带横梁的低维铁电性和狄拉克材料是令人着迷的研究对象。基于第一原理的计算，我们预测了动态稳定的四杆层（QL）XSBO $ _2 $（x = li，na）中自发的面内极化和新型2D紧急费米的共存。根据不同的极化配置，QL-XSBO $ _2 $可以表现出非常规的内部QL铁电性和抗fiferroeleclectricity。这两个地面州都有强大的铁电性，QL-Lisbo $ _2 $和QL-NASBO $ _2 $的自发极化为0.56 NC/m和0.39 nc/m。有趣的是，QL-Lisbo $ _2 $拥有另外两个亚稳态的铁电（FE）阶段，这是带有多个FE订单的第一个2D示例。地面Fe相可以灵活地驱动到两个亚稳态的Fe阶段之一，然后进入抗fiferroelelectric（AFE）阶段。在此阶段过渡期间，在地面Fe相中，出现了几种类型的2D费米，例如，在AFE相中，在地面Fe相，II型II Weyl fermions中的Hourglass Hybrid和II型Weyl环中出现。在自旋轨道耦合下，这些2D费物是可靠的。值得注意的是，以前没有观察到其中两个费米子，例如，沙漏杂种或II型Weyl循环。我们的发现将QL-XSBO $ _2 $确定为研究与2D紧急费米子有关的2D铁电性的独特平台。
Low-dimensional ferroelectricity and Dirac materials with protected band crossings are fascinating research subjects. Based on first-principles calculations, we predict the coexistence of spontaneous in-plane polarization and novel 2D emergent fermions in dynamically stable quadruple-layer (QL) XSbO$_2$ (X= Li, Na). Depending on the different polarization configurations, QL-XSbO$_2$ can exhibit unconventional inner-QL ferroelectricity and antiferroelectricity. Both ground states harbor robust ferroelectricity with enhanced spontaneous polarization of 0.56 nC/m and 0.39 nC/m for QL-LiSbO$_2$ and QL-NaSbO$_2$, respectively. Interestingly, the QL-LiSbO$_2$ possesses two other metastable ferroelectric (FE) phases, demonstrating the first 2D example with multiple FE orders. The ground FE phase can be flexibly driven into one of the two metastable FE phases and then into the antiferroelectric (AFE) phase. During this phase transition, several types of 2D fermions emerge, for instance, hourglass hybrid and type-II Weyl loops in the ground FE phase, type-II Weyl fermions in the metastable FE phase, and type-II Dirac fermions in the AFE phase. These 2D fermions are robust under spin-orbit coupling. Notably, two of these fermions, e.g., an hourglass hybrid or type-II Weyl loop, have not been observed before. Our findings identify QL-XSbO$_2$ as a unique platform for studying 2D ferroelectricity relating to 2D emergent fermions.
