  Strain engineering is one of the most promising and effective routes toward
continuously tuning the electronic and optic properties of materials, while
thermal properties are generally believed to be insensitive to mechanical
strain. In this paper, the strain-dependent thermal conductivity of monolayer
silicene under uniform bi-axial tension is computed by solving the phonon
Boltzmann transport equation with force constants extracted from
first-principles calculations. Unlike the commonly believed understanding that
thermal conductivity only slightly decreases with increased tensile strain for
bulk materials, it is found that the thermal conductivity of silicene first
increases dramatically with strain and then slightly decreases when the applied
strain increases further. At a tensile strain of 4%, the highest thermal
conductivity is found to be about 7.5 times that of unstrained one. Such an
unusual strain dependence is mainly attributed to the dramatic enhancement in
the acoustic phonon lifetime. Such enhancement plausibly originates from the
flattening of the buckling of the silicene structure upon stretching, which is
unique for silicene as compared with other common two-dimensional materials.
Our findings offer perspectives of modulating the thermal properties of
low-dimensional structures for applications such as thermoelectrics, thermal
circuits, and nanoelectronics.
