Review of coherent phonon and heat transport control in one-dimensional phononic crystals at nanoscale

Roman Anufriev,Masahiro Nomura,Jeremie Maire

doi:10.1063/5.0052230

Abstract

Phononic crystals are the acoustic analogs of photonic crystals and aim at manipulating phonon transport using phonon interference in periodic structures. While such periodic structures are typically two-dimensional, many applications require one-dimensional (1D) wire-like or bulk structures instead. In this Research Update, we summarize the past decade of theoretical and experimental studies of coherent control of phonon and heat transport in one-dimensional phononic crystals. At the hypersonic frequencies, phononic crystals successfully found applications in optomechanical devices at the microscale. However, at higher terahertz frequencies, experimentalists struggle to demonstrate that coherent thermal transport at room temperature is possible at length scales of hundreds of nanometers. Although many theoretical works predict a reduction in the thermal conductivity in 1D phononic crystals due to coherent effects, most observations conclude about the incoherent nature of heat conduction at least at room temperature. Nevertheless, experiments on superlattices and carbon nanotubes have demonstrated evidence of coherent heat conduction even at room temperature in structures with the periodicity of a few nanometers. Thus, further miniaturization and improving fabrication quality are currently the main challenges faced by 1D phononic nanostructures.

Highlights

Phonons are the primary carriers of sound, heat, and mechanical vibrations in semiconductors
Being inspired by light manipulations based on the wave interference of photons,1,2 researchers applied a similar approach to manipulations of phonons, as phonons are essentially waves in the atomic lattice. This wave-based approach led to the development of acoustic analogs of photonic crystals called phononic crystals3–5—the artificial structures with periodic boundaries that systematically reflect phonons and cause phonon interference
Theoretical works predict that thermal phonons can become localized in aperiodic superlattices, which leads to the suppression of phonon transport that can theoretically reduce the thermal conductivity by up to two orders of magnitude

Summary

Introduction

Phonons are the primary carriers of sound, heat, and mechanical vibrations in semiconductors. Both the periodicity of the wings and their size can be used to tune the phonon dispersion of the structure, which enables the adjustment of both the frequency and the size of acoustic bandgaps.23 In the two sections, we show how such tuning enables designing complex optomechanical systems and reducing the overall thermal conductivity of nanostructures.

Results

Conclusion