Supersonic thermal excitation-induced shock wave in black phosphorene

Abstract

Thermal transport in low-dimensional materials possesses various novel features since anomalous energy carriers may heavily contribute. Black phosphorene exhibits excellent thermal properties and thus it attracts attention about the possible existence of anomalous energy carriers. In this paper, we find that shockwave appears as a dominant energy carrier in the zigzag direction of black phosphorene when a supersonic thermal excitation above a critical strength is exerted. Comparing with the diffusive thermal transport, shockwave carries a considerable amount of excitation energy and propagates faster than the local acoustic speed. It leads to a strong anisotropic enhancement in the transport speed of thermal energy in the zigzag direction, up to a factor of twofold compared with no shockwave. The linear increase of velocity with intensity and exponential decay of intensity with time of the shockwave are observed. Unlike solitary waves, the collision of shockwaves exhibits no phase shift in the spatial-temporal trajectory. Moreover, it shows that shockwave velocity decreases with tensile strain, which is favorable for modulation. Our results reveal a possible anomalous energy transport process and may help in designing black phosphorene-based thermal devices.