Towards van der Waals Crystal Based Thermal Superconductors

1955年，费米、帕斯塔、乌兰和青岛报道了他们的“令人震惊的小发现”，即单原子链中的激发振动模式不会在很长一段时间内消散成热。这一发现引起了极大的关注，因为它的广泛意义，表明一种类型的热超导体的热导率不断增加的长度。然而，这个概念仍然纯粹是概念性的，半个多世纪以来被认为只有学术意义，因为足够长的单个原子链在实验上仍然是不可能实现的。最近，一项研究表明，超细三硒化铌纳米线的导热系数随着导线长度的增加而增加，超过了42.5微米的纪录水平。这一结果表明，在一类一维材料中实现超高导热系数是可能的。这个项目探索了这些材料中持续发散热传导的条件和极限。本项目的目标是在最近关于Nb三硒化物纳米线的激动人心的发现的基础上，探索准一维van der Waals晶体纳米线中的超扩散输运是否能够持续足够长的长度，最终导致热超导体，即具有比任何已知材料更高的热导值的材料。系统的实验测量将被用来回答关键的科学问题，包括：(1)范德华晶体纳米线中的热传输在什么条件下转变为物理上的一维并成为超扩散？(2)这些纳米线中的超扩散传输的长度限制是多少，我们如何扩展这个限制？(3)是否有可能通过沿线轴诱导弹性硬化来创造具有可调热性能的新型纳米材料，从而促进一维热传输。该项目的学术价值在于对范德华晶体纳米线中热输运的基本理解。此外，回答这些材料中热传输的超扩散性质是否能够持续足够长的时间以提供一类能够改变要求高效散热的各种工程实践的热超导体的问题具有实际意义。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.