Anderson Localization Quenches Thermal Transport in Aperiodic Superlattices

Abstract

We show that aperiodic superlattices exhibit intriguing interplay between phononic coherent wave interference effects and incoherent transport. In particular, broadband Anderson localization results in a drastic thermal conductivity reduction of 98% at room temperature, providing an ultralow value of 1.3 W m −1 K −1 , and further yields an anomalously large thermal anisotropy ratio of ∼10 2 in aperiodic Si=Ge superlattices. A maximum in the thermal conductivity emerges as an unambiguous consequence of phonon Anderson localization at a system length scale bridging the extended and localized transport regimes. The frequency-resolved picture, combined with our lattice dynamical description of Anderson localization, elucidates the rich transport characteristics in these systems and the potential of correlated disorder for sub-to few-THz phononic engineering of heat transport in thermoelectric applications.

Heat Transport Control and Thermal Characterization of Low-Dimensional Materials: A Review

“…Ultralow values of k were also reported by Juntunen et al [68] in aperiodic Si:Ge SLs. The authors explained their observation in terms of wide range Anderson localization, which leads to a destructive interference of coherent phonons and consequently a drastic reduction of k by quenching the wave transport under structural disorder.…”

Heat current anticorrelation effects leading to thermal conductivity reduction in nanoporous Si

“…Most often, the phonon-gas picture suffices to describe thermal conductivity, even in nanoporous materials [14][15][16]. However, the issue as to whether 'coherent' wave effects alter the phonon dispersion relationschanging group velocities, the density of states, and creating phononic bandgapsor result in the localization of modes is still an open topic [6,[16][17][18][19]. Herein, we report on the emergence of anticorrelated (AC) specular phonon scattering (and thus heat flux) as a result of heat trapping between the pores, which can provide up to ~ 80% additional reduction in thermal conductivity for specific nanoporous geometries.…”

Thermal conductivity suppression in GaAs–AlAs core–shell nanowire arrays

“…A similar reduction is also observed in the AlGaAs surface-alloyed NWs within experimental uncertainty, suggesting that the thermal conductivity reduction induced by the thin shell is predominantly related to the Rayleigh-type scattering of high-frequency phonons with the characteristic τ i ∝ ω −4 dependence. 47 A more moderate reduction may thus result from the relative shift from resonant phonon inhibition to impurity scattering mediated by the shell in NWs with a thick GaAs core. The former is indeed expected to be mitigated with the increasing core diameter, resulting in thermal conductivity reduction primarily due to the interface and alloy scattering.…”