When heat flows backwards: A neat solution for hydrodynamic heat transport
When we think about heat travelling through a material, we typically picture diffusive transport, a process that transfers heat from high-temperature to low-temperature as particles and molecules bump into each other, losing kinetic energy in the process. But in some materials heat can travel in a different way, flowing like water in a pipeline that – at least in principle – can be forced to move in a direction of choice. This second regime is called hydrodynamic heat transport.
Heat conduction is mediated by movement of phonons, which are collective excitations of atoms in solids, ...