EFRI NewLaw: Controlling Thermal Transport with Topologically Guided Heat Carriers

Purdue University, West Lafayette IN

Investigators

Abstract

This project investigates novel ways to transport, guide and direct thermal energy (heat) based on the new paradigm of topological thermal transport. Through this paradigm, heat can be guided to flow only along the boundary of a material while avoiding its interior, as well as in a highly directional ways that are also robust to material disorder and other defects. To achieve this, the team will harness and engineer special topological properties of materials and devices involving various heat carriers including electrons, phonons (crystal lattice vibrations) or light. Discoveries and innovations from this project could impact many technological areas involving the control and transport of thermal energy, such as on-chip heat management and cooling in modern electronic and photonic systems, as well as energy generation, conversion and harvesting through thermoelectrics and photothermovoltaics. The project could also lead to new schemes for thermal management such as thermal insulation, ?cloaking? and directed thermal flow. The research team will contribute to an online forum called ?Thermal Hub? within NSF-funded NanoHub that counts millions of subscribers and users. The forum is expected to facilitate sharing and exchange of information in the emerging field of ?topological thermal transport?, and benefit research and development in nanoscale thermal engineering in general. Both graduate and undergraduate students will be actively involved in the research and learning activities of the program. Particular attention will be placed on broadening the participation of women & minority students via various diversity and outreach activities by the team. The project will leverage several existing programs at their institutions and partnerships with several undergraduate and minority colleges. Topological states of electrons such as quantum Hall effect (QHE) and topological insulators (TI) are some of the most important developments in contemporary condensed matter physics. Such topological electronic states feature topologically-protected electronic transport along the boundary of an insulating bulk sample that is immune to scattering by various impurities. This project will pursue topological concepts in the so-far-unexplored realm of thermal transport. The proposed approach will harness or engineer topological properties of three different types of heat carriers ? electrons, phonons and phonon-polaritons, to realize topologically guided and protected thermal transport that can be further controlled by external forces and fields. The first theme of the program will explore high-quality electronic topological insulators with insulating bulk and conducting topological surface states of spin-helical Dirac electrons to demonstrate optically and magnetically controlled, and non-reciprocal electronic thermal conduction, and other novel thermal transport carried by such topological surface electrons. The second and third themes of the project will focus on the extension and analogs of several key physical mechanisms underlying the electronic topological states --- such as spin-momentum coupling/locking, chirality/valley states, and spin/valley Hall effects --- to phonons and hybrid phonon-photon polaritons, toward realizing various topological phononic states and phonon/thermal transport.