Active control of thermal conductivity of low-dimensional <b> <i>α</i> </b>-PbS by strain-induced ferroelectric

Active control of heat transfer in nanostructured materials is crucial for the development of microelectronic devices. Thermal switch is a typical heat management device, which has attracted widespread attention. In this work, based on first-principles calculations, we propose a two-dimensional thermal switch based on the strain-induced ferroelectric phase transition in α-PbS. It is found that thermal conductivity can be significantly reduced by external strain and a room temperature two-dimensional thermal switch with a switch ratio of 3.7 can be constructed. The calculated phonon lifetime and scattering rate reveal that phonons around 2 THz frequency range predominantly contribute to the modulation in thermal conductivity when the strain is smaller than 2.0%. A detailed analysis on phonon dispersion indicates that these phonons are LO2 and TO3 branches. When the strain is larger than 2.0%, the decrease in phonon group velocity leads to the reduction in thermal conductivity. Our work elucidates the mechanisms for changes in the thermal conductivity of α-PbS under strain and provides a low-dimensional thermal switch, which is promising for future applications in microelectronic devices.