范德华耦合双壁碳纳米管系统中一维物理的定量研究

Nanoscale electronic coupling governs many important physical processes, ranging from charge separation in heterojunctions to energy transfer in photosynthesis. In bulk materials, such nanoscale coupling is usually achieved through strong chemical bonding. In low dimensional materials, van der Waals coupling can play an important role because electron waves are often exposed at the surfaces. Recently there has been tremendous interest to study emerging phenomena in van der Waals-coupled two-dimensional (2D) materials, such as van Hove singularity in twisted graphene bilayers and Hofstadter butterfly in graphene/boron nitride heterostructures. Physics in van der Waals-coupled one-dimensional (1D) materials can be equally rich and exciting, due to the unique strong quantum confinement and enhanced electron-electron interactions. Double-walled carbon nanotubes (DWNTs) provide an ideal family of model system to explore new 1D physics arising from van der Waals interactions. Here I propose to investigate novel 1D phenomena arising from van der Waals coupling in different DWNTs through a combination of single-tube level structural determination and high-contrast nano-optics/spectroscopy. In particular, we will focus on three exciting directions: (1) Electronic structure renormalization in incommensurate DWNTs (due to Van der Waals coupling); (2) Coupling between excitons and Luttinger liquid in metal/semiconductor DWNTs (i.e. DWNTs composed of a metallic outer wall and a semiconducting inner wall); (3) Ultrafast energy transfer between the inner- and outer-wall nanotubes. The understanding of electronic coupling in DWNTs can also lead to new ways to manipulate and control the electronic structure of 1D carbon nanotubes exploiting the van der Waals interactions. It may enable novel nanoelectronic and nanophotonic applications based on carbon nanotubes. In addition, the principles will be also applicable in other low-dimensional materials.

宏观体材料的性质主要由强化学键决定；低维纳米材料由于电子态主要分布在表面，弱范德华耦合可以对材料性质起到决定性影响。最近在范德华耦合的二维石墨烯\石墨烯、石墨烯\氮化硼双原子层中已经发现了新奇的范霍夫奇点态和霍夫施塔特蝴蝶图形效应。范德华耦合的一维体系中由于存在量子尺寸效应和增强的电子-电子多体相互作用，可能存在全新的一维物理现象。 本项目拟采用范德华耦合的一维模型体系双壁碳纳米管为研究对象，利用和发展透射电镜+超高灵敏度超快纳米光学技术原位研究单个碳纳米管水平上的手性结构和光谱，探索范德华电子耦合对一维体系电子结构的影响、激子-拉廷格液体相互作用、两层碳纳米管间超快电荷转移等一维物理问题。上述研究结果将为利用范德华作用调控碳纳米管的电子学、光学等物理性质和开发新一代碳纳米管基的纳米电子学、光子学器件提供理论基础。项目中发展的原位结构和光学性质测量方法也可以应用到其它低维纳米体系。

本项目围绕研究计划，采用范德华耦合的一维模型体系双壁碳纳米管为研究对象，发展了透射电镜+超高灵敏度超快纳米光学技术，原位研究了单根碳纳米管及碳纳米管阵列的光谱及生长方面的科学问题。利用发展的原位透射电镜与超高灵敏度偏振显微技术，首次开发了手性椭偏光干涉检测方法，实现了对单根原子结构确定的单壁碳纳米管光学复极化率的测量（Nature Communications 2018, 9, 3387），该工作入选中国激光杂志社评选的2018年中国光学十大进展候选；发展了水平阵列碳纳米管结构统计信息快速光学成像表征方法（Advanced Materials 2016, 28, 2018）、单个碳纳米管刻蚀的原位光学表征方法（Advanced Materials 2017, 29, 1701959）、单个碳纳米管超快声子动力学谱技术（Nano Letters 2018, 18, 2590）、基于碳纳米管量子隧穿效应的可见光场致电子发射（Advanced Materials 2017, 29, 1701580）；绘制了的单壁碳纳米管从600-2400 nm非线性吸收性质的宽频衰减图（Nanoscale 2016, 8, 9304）；并利用矢量光场调控单根碳纳米管的拉曼响应（Optical Letters 2017, 42, 13）等。这些技术极大地推动了碳纳米管原位光学成像和光谱表征领域的发展。此外，将发展技术应用到二维范德华耦合材料体系。实现了世界纪录的超快单晶石墨烯生长(Nature Nanotechnology 2016, 11, 930)，科技部及国家自然科学基金委都对其进行了报道，并入选纳米人网站评选的2016年世界石墨烯十大进展。还利用范德华作用调控二维材料的电子学、光学等物理性质（Nature Communications 2014, 5, 4966; ACS Nano 2015, 9, 6478; JACS 2018, 140, 14952; Nature Communication 2016, 7, 12334; JACS 2015, 137, 7994），为开发新一代的纳米电子学、光子学器件提供理论基础。