Towards van der Waals Crystal Based Thermal Superconductors

1955年，费米、帕斯塔、乌拉姆和钦古报告了他们“令人震惊的小发现”，即单原子链中的激发振动模式在很长一段时间内不会消散为热量。这一发现由于其广泛的影响而引起了极大的关注，这表明了一种热超导体的热导率随着长度的增加而不断增加。然而，这个概念仍然是纯粹的概念，并被视为只有学术兴趣超过半个世纪，因为单原子链足够长的实验仍然无法实现。最近，一项研究表明，超薄三硒化铌纳米线的热导率随着线长的增加而增加，超过了42.5 μm的创纪录水平。这一结果表明，在一类一维材料中实现导热系数的可能性。本项目旨在探索这些材料中持续发散热导率的条件和限制。基于最近关于三硒化铌纳米线的令人兴奋的发现，本项目的目标是探索准一维货车德瓦尔斯晶体纳米线中的超扩散输运是否可以持续到足够长的长度，最终导致热超导体，即，热导率值高于任何已知材料的材料。将进行系统的实验测量来回答关键的科学问题，包括：（1）在什么条件下，货车德瓦尔斯晶体纳米线的热传输过渡到物理一维，并成为超扩散？(2)在这些纳米线中，超扩散输运的长度极限是什么？我们如何扩展这个极限？(3)是否有可能通过沿沿着丝轴诱导弹性硬化来产生具有可调热性能的新型纳米材料，所述弹性硬化促进一维热传输。该项目的智力价值在于对货车德瓦尔斯晶体纳米线中的热传输的基本理解。此外，回答这些材料中热输运的超扩散性质是否能持续足够长的时间以提供一类热超导体的问题也具有实际意义，该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的评估被认为值得支持。影响审查标准。

In 1955, Fermi, Pasta, Ulam, and Tsingou reported their “shocking little discovery” that an excited vibration mode in single atomic chains did not dissipate into heat over a long period of time. This finding attracted tremendous attention due to its broad implications, suggesting a type of thermal superconductors of ever-increasing thermal conductivity with length. However, the concept remains purely conceptual and is regarded as only of academic interest for more than a half century, because single atomic chains of sufficient length remain experimentally unattainable. Recently, a study has shown that the thermal conductivity of ultra-thin niobium triselenide nanowires increases with the wire length beyond a record level of 42.5 µm. This result indicates a possibility of achieving ultrahigh thermal conductivity in a class of one-dimensional materials. This project explores the conditions and limits of persistent divergent thermal conductivity in these materials.Building on the recent exciting discovery with niobium triselenide nanowires, the objective of this project is to explore whether superdiffusive transport in quasi-one-dimensional van der Waals crystal nanowires can persist to sufficient length that will eventually lead to thermal superconductors, i.e., materials with thermal conductivity values higher than that of any known materials. Systematic experimental measurements will be conducted to answer key scientific questions including: (1) under what conditions thermal transport in van der Waals crystal nanowires transitions into physically one-dimensional and becomes superdiffusive? (2) What is the length limit of superdiffusive transport in these nanowires and how can we extend the limit? (3) Whether it is possible to create novel nanomaterials with tunable thermal properties through induced elastic stiffening along the wire axis that promotes one dimensional thermal transport. The intellectual merit of the project resides in the fundamental understanding of thermal transport in van der Waals crystal nanowires. In addition, it is of practical significance to answer the question of whether the superdiffusive nature of thermal transport in these materials can persist over sufficient length to provide a class of thermal superconductors, which can transform various engineering practices that request efficient heat dissipation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.