Two-dimensional materials can conduct heat very well due to how phonons move around. This study looked at how heat moves at boundaries and interfaces in these materials. They used computer simulations to see how heat flows in different situations. They found that at interfaces, heat can move from cold areas to hot areas, which is unusual. They also came up with two models to explain these findings: one that follows how phonons move, and another that separates different types of heat flow at boundaries.