(color online) (a) Thermal rectification ration of the two kinds of graded nanowire. Heat current versus temperature difference Δ is also given in the insets. (b) Structure and temperature profile of a pure InAs nanowire with wider steps, Δ=−0.3. The As and In atoms are identified by brown and orange, respectively. Reprinted with permission from Ref. [135]. Copyright (2014) by AIP Publishing LLC.