Quantized Phonon Conductance of One-dimensional Systems

Non-technical Abstract: The ability of a solid to conduct electricity and heat determines its application potential in new technologies such as microelectronics. Surprisingly, quantum physics predicts that the electricity- and heat- carrying capabilities of a solid at the nanometer scale do not reduce continuously with decreased cross-section. This quantum theory has been validated repeatedly in different experiments for both the electricity- and heat-carrying capabilities of electrons in different nanostructures. In comparison, there has been only one reported experimental observation of the predicted quantum behavior of the heat-carrying ability in a polycrystalline silicon nitride nanostructure. In response to a call for further experimental investigations of the quantum theory of lattice heat transport, this project is focused on experimental investigation of this quantum theory in individual single-walled carbon nanotubes with the use of a unique measurement method. Success of this research is expected to both enhance the understanding of a essential pillar of condensed matter physics and provide education and outreach opportunities for broadening the participation in quantum and thermal science research and technology developments. Technical Abstract: Free of two-level defects, SWCNTs are closest to an ideal one-dimensional (1D) quantum system among the nanostructures that have been experimentally realized. The goal of this work is to advance multiprobe measurements of the intrinsic thermal conductance of 1D nanostructures for accurate detection of the quantized phonon conductance that has been predicted for a SWCNT at a relatively high temperature up to about 10 K. This temperature range is much more conducive to producing unambiguous experimental evidence of quantized phonon conductance than the below-0.8 K temperature required for prior studies of silicon nitride nanobeams. If successful, the proposed measurements of SWCNTs will establish an experimental capability for detecting and controlling quantized phonon transport behaviors of low-dimensional systems. This capability is expected to advance the frontier of experimental research in a foundational area of condensed matter physics. 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.