Towards van der Waals Crystal Based Thermal Superconductors

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.