电荷密度波材料（TaSe4）2 I中表面电荷诱导的Dirac带分裂
Surface Charge Induced Dirac Band Splitting in a Charge Density Wave Material (TaSe4)2I
摘要：
（TaSe 4）2 I是一种准一维（1D）晶体，具有温度驱动的金属-绝缘体相变特征。在电荷密度波（CDW）温度Tc以上，（TaSe 4）2 I已被预测为具有Weyl半金属相。在Tc以下，它变成了轴子绝缘体。在（TaSe_4）_2 I的（110）面上进行了角分辨光电子能谱（ARPES）测量，在第一布里渊区观察到了两组Dirac类能带，这与我们的第一性原理计算吻合得很好.此外，我们发现，每个狄拉克带在某些情况下表现出数百meV的能量分裂。结合芯能级测量，我们的理论分析表明，这种狄拉克带分裂是由于表面碘原子的损失引起的表面电荷极化的结果。我们的研究结果为Peierls化合物能带拓扑和CDW有序之间的相互作用提供了新的线索，并将激发对强关联准一维材料拓扑性质的更多研究。
英文摘要：
(TaSe4)2I, a quasi-one-dimensional (1D) crystal, shows a characteristic temperature-driven metal-insulator phase transition. Above the charge density wave (CDW) temperature Tc, (TaSe4)2I has been predicted to harbor a Weyl semimetal phase. Below Tc, it becomes an axion insulator. Here, we performed angle-resolved photoemission spectroscopy (ARPES) measurements on the (110) surface of (TaSe4)2I and observed two sets of Dirac-like energy bands in the first Brillion zone, which agree well with our first-principles calculations. Moreover, we found that each Dirac band exhibits an energy splitting of hundreds of meV under certain circumstances. In combination with core level measurements, our theoretical analysis showed that this Dirac band splitting is a result of surface charge polarization due to the loss of surface iodine atoms. Our findings here shed new light on the interplay between band topology and CDW order in Peierls compounds and will motivate more studies on topological properties of strongly correlated quasi-1D materials.
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