Structural Distortions and Charge Density Waves in Iodine Chains Encapsulated inside Carbon Nanotubes
Structural Distortions and Charge Density Waves in Iodine Chains Encapsulated inside Carbon Nanotubes
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DOI：
10.1021/acs.nanolett.7b00969
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发表时间：
2017-06-01
期刊：
影响因子：
10.8
通讯作者：
Krasheninnikov, Arkady V.
中科院分区：
文献类型：
--
作者：
Komsa, Hannu-Pekka;Senga, Ryosuke;Krasheninnikov, Arkady V.
原子链是获得一维金属中电子动力学和电子自由度与离子自由度耦合的基本见解的完美系统。根据带填充的不同，它们可以表现出佩尔斯不稳定性（或电荷密度波），其中具有部分填充带的等间距原子链本质上是不稳定的，表现出晶格的自发扭曲，进一步导致系统中的金属绝缘体转变。在这里，我们使用高分辨率扫描透射电子显微镜，直接对碳纳米管内的碘原子链的原子结构进行成像。除了长等距链外，还观察到由碘二聚体和三聚体组成的链，以及它们之间的过渡。第一性原理计算再现了实验中观察到的键长和晶格常数，表明离子运动在纵向上基本上不受限制，而在横向上自然受到纳米管的限制。此外，三聚链具有电荷密度波的特征。这种转变是由链和纳米管之间电荷转移的变化驱动的，并由纳米管提供的电荷补偿和额外的筛选实现。
Atomic chains are perfect systems for getting fundamental insights into the electron dynamics and coupling between the electronic and ionic degrees of freedom in onedimensional metals. Depending on the band filling, they can exhibit Peierls instabilities (or charge density waves), where equally spaced chain of atoms with partially filled band is inherently unstable, exhibiting spontaneous distortion of the lattice that further leads to metal insulator transition in the system. Here, using high-resolution scanning transmission electron microscopy, we directly image the atomic structures of a chain of iodine atoms confined inside carbon nanotubes. In addition to long equidistant chains, the ones consisting of iodine dimers and trimers were also observed, as well as transitions between them. First-principles calculations reproduce the experimentally observed bond lengths and lattice- constants, showing that the ionic movement is largely unconstrained in the longitudinal direction, while naturally confined bythe nanotube in the lateral directions. Moreover, the trimerized chain bears the hallmarks of a charge density wave. The transition-is driven by changes in the charge transfer between the chain and the nanotube and is enabled by the charge compensation and additional screening provided by the nanotube.