Chirality Enables Thermal Magnon Transistors

We report a theory of thermal spin pumping into proximity magnets under a transverse-bias-driven heat flow of magnons in magnetic films when the dipolar coupling to the magnetic gate is tuned to be "chiral". While there is no rectification of the magnon current in the film, we predict that chirality diverts a large percentage (50$\%$ for perfect chirality) of it into the gate. This transverse thermal spin pumping effect can be controlled by rotating the film magnetization and may help manage the heat flow in future magnonic circuits.