Phonon coherence and its effect on thermal conductivity of nanostructures

Abstract

The concept of coherence is one of the fundamental phenomena in electronics and optics. In addition to electron and photon, phonon is another important energy and information carrier in nature. Without any doubt, exploration of the phonon coherence and its impact on thermal conduction will markedly change many aspects in broad applications for heat control and management in the real world. So far, the application of coherent effect on manipulation of phonon transport is a challenging work. In this article, we review recent advances in the study of the phonon coherent transport in nanomaterials and nanostructures. We first briefly look back the classical and quantum theory of coherence. Next, we review the progresses made in the understanding of phonon coherence in superlattice, nanowires and nanomeshes, respectively, and focus on the effect of phonon coherence on thermal conductivity. Finally, we introduce the recent advances in the direct detection of phonon coherence using optical coherence theory. ARTICLE HISTORY

Thermal Transport in 3D Nanostructures

“…From the perspective of coherent phonon transport, the thermal conductivity would be reduced due to the resulting phononic bandgaps and the reduced group velocities. [99] Several works have argued the role of coherent phonons on the thermal transport of holey nanostructures, [25,96,100] and the range of occurrence of the phonon interference is still an open question. In a recent work, Maire et al show the thermal conduction controlled by coherence in Si holey nanostructures over a relatively large temperature range, until the transition to purely diffusive heat conduction was observed at 10 K. [100a] With recent advances of nanofabrication technology, it is expected that the working temperature range of phononic crystals can be further broadened.…”

“…The phonon coherence has already been demonstrated to result in remarkably reduced thermal conductivity in phononic crystals, which opens up a new and pro mising avenue to construct high-performance TE devices. [99]…”

Thermal Conductivity of Amorphous Materials

“…Clearly, these various technological aspects, including thermal protection, advanced sensors, and thermoelectric devices, drive tremendous interest in the discovery of low thermal conductivity materials. [9,[14][15][16][17][18][19] Amorphous semiconductors are commonly used in numerous electronic and optoelectronic devices, for example, Figure 1. The illustration of applications of amorphous solids and the expected thermal property in these applications.…”

Significant enhancement of the thermoelectric properties of CaP3 through reducing the dimensionality

“…However, optimizing simultaneously these transport parameters is an arduous process due to the complex competition among them, which greatly limits the TE performance of materials 7 . In the past few years, in order to regulate and control these complex parameters, band structure engineering 8,9 and quantum confinement effect 10 are devoted to optimize electric transport coefficients, while other effects are presented to reduce κ l through phononic crystal patterning 11,12 or dimensionality reduction 13 . Generally, inherent low κ l is a crucial precondition for achieving high TE performance, because it can remain slightly variation when optimizing the electrical coefficients.…”