2 H- NbS2中杂质钉扎的无公度电荷密度波和局域声子激发
Impurity-pinned incommensurate charge density wave and local phonon excitations in 2H-NbS2
摘要：
本文报道了2 H-NbS 2超导态的扫描隧道显微镜（STM）和光谱学（STS）研究。我们直接可视化了原子杂质钉扎的无公度电荷密度波的存在。在强隧穿条件下，来自STM针尖的电场使无公度CDW与杂质脱离钉扎。我们利用STM非弹性隧穿谱（IETS）技术探测了2 H-NbS 2中的声子激发，并测量了原子杂质对局域声子激发的影响。与2 H-NbS_2的振动态密度计算结果相比，发现了两个声子激发分支，分别对应于Nb离子和S离子的振动，且局域声子激发强度对原子杂质不敏感。我们的研究结果证实了2 H-NbS 2中无公度CDW和超导电性的共存，并为利用STM IETS探测过渡金属二硫族化合物中原子尺度的声子激发开辟了新的途径.
英文摘要：
Here we report a scanning tunneling microscopy (STM) and spectroscopy (STS) study in the superconducting state of 2H-NbS2. We directly visualize the existence of incommensurate charge density wave (CDW) that is pinned by atomic impurities. In strong tunneling conditions, the incommensurate CDW is de-pinned from impurities by the electric field from STM tip. We perform STM-based inelastic tunneling spectroscopy (IETS) to detect phonon excitations in 2H-NbS2 and measure the influence of atomic impurities on local phonon excitations. In comparison with the calculated vibrational density of states in 2H-NbS2, we find two branches of phonon excitations which correspond to the vibrations of Nb ions and S ions, and the strength of the local phonon excitations is insensitive to the atomic impurities. Our results demonstrate the coexistence of incommensurate CDW and superconductivity in 2H-NbS2, and open the way of detecting atomic-scale phonon excitations in transition metal dichalcogenides with STM-based IETS.
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