Heat conduction in low-dimensional materials has attracted recent interests for the applications in thermal management and thermoelectrics. Among them, periodic structures have been extensively investigated recently due to the wave-particle duality of phonons. For the multilayer structures under the same system length and interface density, the periodic arrangement of interfaces in perfect SL structure seems to be the best option for heat conduction, since a suppressed thermal transport has been observed in various studies when introducing randomness to the perfect periodic structures due to the emergence of phonon localization.
We investigate the thermal transport properties of three kinds of multilayer structures: a perfect superlattice (SL) structure, a quasi-periodic multilayer structure consisted of two superlattice (2SL) structures with different periods, and a random multilayer (RML) structure. Our simulation results show that there exists a large number of aperiodic multilayer structures that have effective thermal conductivity higher than that of the SL counterpart, showing enhancement ratio in the effective thermal conductivity up to 193%. Surprisingly, some RML structures also exhibit enhanced thermal transport than the SL counterpart even in the presence of phonon localization. The detailed analysis on the underlying mechanism reveals that such peculiar enhancement is caused by the synergistic effect of coherent and incoherent phonon transport, which can be tuned by the structural configuration. Combined with molecular dynamics simulations and the machine learning technique, we further reveal that the enhancement effect of the effective thermal conductivity by 2SL structure is more significant when the period of SL structure is close to the critical transition period between the coherent and incoherent phonon transport regimes. Our study proposes a novel strategy to enhance the thermal transport in multilayer structures by regulating the wave-particle duality of phonons via the structure optimization, which might provide valuable insights to the thermal management in devices with densely packed interfaces.
Fig. 1 Schematic graphs for the three types of multilayer structures and NEMD setup. The dark and light regions represent material A and B, respectively. (a) SL structure with period length of P0 and number of layers of N0. (b) 2SL structure combined by two SL structures with different period lengths (P1 and P2) and number of layers (N1 and N2). R1 is the ratio of the left region. (c) RML structure. (d) Schematic setup for the NEMD simulations.
DOI: 10.1007/s11467-022-1170-5
