标题： 拓扑绝缘体单层WTe2中电荷密度波激子序参量的观测 显示英文标题

标题： Observation of charge density wave excitonic order parameter in topological insulator monolayer WTe2

摘要： 强电子-空穴相互作用在半金属或窄带隙半导体中可能驱动凝聚激子的基态。单层WTe2被提议作为这种激子凝聚体的宿主材料，但宏观量子相干凝聚体的关键标志——序参量——尚未被观测到。在这里，我们使用傅里叶变换扫描隧道光谱（FT-STS）研究单层WTe2中的准粒子散射（QPI）和局域态密度（LDOS）的周期性调制。在石墨烯上的WTe2中，载流子密度可以通过背栅调节，在这种情况下，FT-STS显示二维体带中的QPI特征，证实了中性WTe2中能隙的相互作用性质以及高度n型和p型掺杂WTe2的半金属性质。我们在金属衬底（石墨烯和石墨）上中性WTe2的拓扑边缘模式上观察到LDOS的额外非色散空间调制，我们将其解释为由于金属衬底的屏蔽效应，低相互作用强度下拓扑边缘模式与预期的激子凝聚体的电荷密度波序参量之间的相互作用。 显示英文摘要

摘要： Strong electron-hole interactions in a semimetal or narrow-gap semiconductor may drive a ground state of condensed excitons. Monolayer WTe2 has been proposed as a host material for such an exciton condensate, but the order parameter - the key signature of a macroscopic quantum-coherent condensate - has not been observed. Here we use Fourier-transform scanning tunnelling spectroscopy (FT-STS) to study quasi-particle interference (QPI) and periodic modulations of the local density of states (LDOS) in monolayer WTe2. In WTe2 on graphene, in which the carrier density can be varied via back-gating, FT-STS shows QPI features in the 2D bulk bands, confirming the interacting nature of the bandgap in neutral WTe2 and the semi-metallic nature of highly n- and p-doped WTe2. We observe additional non-dispersive spatial modulations in the LDOS imprinted on the topological edge mode of neutral WTe2 on metallic substrates (graphene and graphite), which we interpret as the interaction of the topological edge mode with the expected charge density wave order parameter of the excitonic condensate in WTe2 at low interaction strength due to screening by the metallic substrates.