Figure 4. Explanation of the physical mechanism for the thermal rectification.

(Case I) Heat flows from the region without pores to the modified nanopore region. (Case II) The heat flow direction is reversed from the nanopore region to the region without pores, where the letters H and C indicate the hot and cold sensors. In the λ-T curves, the black dashed lines represent the thermal conductivity of monolayer graphene. The higher line is the thermal conductivity of graphene without pores, while the lower line is the thermal conductivity of graphene with nanopores. The red thick lines that overlap the black dashed lines represent the temperature-dependent thermal conductivity of the asymmetric monolayer graphene with nanopores. The total thermal conductivity, λ_{case II}, is larger than λ_{case I}.