Biaxial tensile strain tuned up-and-down behavior on lattice thermal conductivity in $\beta$-AsP monolayer

Abstract

Various two-dimensional (2D) materials with graphene-like buckled structure emerge, and the $\beta$-phase AsP monolayer has been recently proposed to be thermodynamically stable from first-principles calculations. The studies of thermal transport are very useful for these 2D materials-based nano-electronics devices. Motivated by this, a comparative study of strain-dependent phonon transport of AsP monolayer is performed by solving the linearized phonon Boltzmann equation within the single-mode relaxation time approximation (RTA). It is found that the lattice thermal conductivity ($\kappa_L$) of AsP monolayer is very close to one of As monolayer with similar buckled structure, which is due to neutralization between the reduce of phonon lifetimes and group velocity enhancement from As to AsP monolayer. The corresponding room-temperature sheet thermal conductance of AsP monolayer is 152.5 $\mathrm{W K^{-1}}$. It is noted that the increasing tensile strain can harden long wavelength out-of-plane (ZA) acoustic mode, and soften the in-plane longitudinal acoustic (LA) and transversal acoustic (TA) modes. Calculated results show that $\kappa_L$ of AsP monolayer presents a nonmonotonic up-and-down behavior with increased strain. The unusual strain dependence is due to the competition among reduce of phonon group velocities, improved phonon lifetimes of ZA mode and nonmonotonic up-and-down phonon lifetimes of TA/LA mode. It is found that acoustic branches dominate the $\kappa_L$ in considered strain range, and the contribution from ZA branch increases with increased strain, while it is opposite for TA/LA branch. By analyzing cumulative $\kappa_L$ with respect to phonon mean free path (MFP), tensile strain can modulate effectively size effects on $\kappa_L$ in AsP monolayer.