Agenda

Résumé : Heat conduction control in a semiconductor membrane by nanostructuring will be discussed from the viewpoint of photonics. We classify the systems by similarity, difference, and hybridization of phonons and phonons, and explain characteristic thermal phonon transport in each system. Prospects of thermal phonon engineering will be also discussed. Light propagation in ray optics and thermal phonon transport at the nanoscale are similar due to ballisticity. The characteristic propagation of light and mechanical vibrations in band-engineered periodic structures, i.e. photonic and phononic crystals, derives from the wave properties of electromagnetic and elastic waves [1]. Some recent work on the control of heat conduction by well-designed nanostructures are taken up to discuss how we can design nanostructures to control heat transport more effectively by considering the similarity and difference of photons and thermal phonons [2]. The ballistic behavior of phonons in their mean free path (MFP) allows advanced heat flux control such as directional heat flux and heat focusing. This thermal phonon behavior is similar to ray optics and is therefore named “Ray phononics” [3]. The selection of phonon k-vector direction by aligned nanoholes formed in a membrane result in the formation of directional heat flux. The directional heat flux is maintained within the MFP of thermal phonons. The interaction and hybridization of photons and phonons are also interesting and will lead to new functionality. Phonons can control the emission of a single photon from a quantum dot embedded in a high-Q optical micro/nanocavity [4, 5].
Regarding hybridization, phonons can travel faster by four orders of magnitude by shaking hands with photons: forming surface phonon polaritons (SPhPs). In addition, “phonon” scattering is strongly suppressed by the dressing of the electromagnetic wave, resulting in the enhancement of thermal conduction in thin dielectric membranes. This dramatic change in thermal energy transport property by SPhPs opens up new possibilities for thermal management in thin membranes [6]. The hydrodynamic behavior of phonons is an example of a different transport phenomenon that is a phenomenon rarely observed in optics. The collective behavior, which exists in electronic and phononic systems due to interaction, of phonons provides interesting thermal transport such as phonon Poiseuille flow [7]. We demonstrate the first thermal Tesla valve [8].
References
[1] J. Ravichandran, et al., Nat. Mater., 13, 168 (2014).
[2] M. Nomura, et al., Mater. Today Phys. 22, 100613 (2022). [Review paper]
[3] R. Anufriev and M. Nomura, Mater. Today Phys. 15, 100272 (2020).
[4] M. Nomura, Nat. Nanotechnol., 11, 496 (2016).
[5] M. Nomura, et al., Nat. Phys. 6, 279 (2010).
[6] Y. Wu, et al., Sci. Adv. 6, eabb4461 (2020).
[7] X. Huang, et al., Nat. Commun., 14, 2044 (2023).
[8] X. Huang, et al. Nature 634, 1086 (2024).
Figure 1. Discusses thermal phonon transport, categorizing
photon and phonon similarities, differences, and hybridization.