Spin caloritronics of a quantum dot coupled to a magnetic insulator and normal metal

We investigate the generation of spin current through temperature gradients in a quantum dot-based hybrid system. In particular, we study a quantum dot coupled to a magnetic insulator and a (non)magnetic metallic electrode. Generally, each electrode is maintained at a different temperature, resulting in a finite spin current. In this system, spin current of the magnonic type is converted into electric spin current, and vice versa, depending on the direction of the temperature gradient. We examine the influence of the magnonic energy-dependent density of states and many-body magnon interactions on thermally induced spin current. Additionally, the system can work as a spin Seebeck engine, converting heat into spin current. We establish the conditions under which the system operates as a heat engine and present results on its performance. Furthermore, we propose a device based on the system that acts as an efficient thermal spin-diode-allowing spin current to pass in one direction of the temperature bias while completely suppressing it in the opposite direction.