Towards van der Waals Crystal Based Thermal Superconductors

1955年，费米、意大利面、乌拉姆和Tsingou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。这一发现因其广泛的意义而引起了极大的关注，它提示了一种热导率随长度不断增加的热超导体。然而，这个概念仍然纯粹是概念性的，半个多世纪以来只被认为是学术上的兴趣，因为足够长度的单原子链在实验上仍然无法实现。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超过42.5µm的记录水平而增加。这一结果表明了在一类一维材料中实现超高导热性的可能性。该项目探索了这些材料中持续发散导热性的条件和限制。基于最近对三硒化铌纳米线的激动人心的发现，本项目的目标是探索准一维范德华晶体纳米线中的超扩散输运能否持续到足够长的长度，从而最终导致热超导体，即导热系数高于任何已知材料的材料。系统的实验测量将回答关键的科学问题，包括：(1)在什么条件下，范德华晶体纳米线中的热输运转变为物理一维并成为超扩散？(2)这些纳米线的超扩散输运的长度极限是什么？我们如何延长这个极限？(3)是否有可能通过诱导沿线轴的弹性硬化来促进一维热输运来制造具有可调热性能的新型纳米材料。该项目的智力价值在于对范德华晶体纳米线的热输运有了基本的了解。此外，回答这些材料中热输运的超扩散性质是否能够持续足够长的时间以提供一类热超导体，从而改变要求高效散热的各种工程实践的问题具有实际意义。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.