Conventional solid-state thermoelectric devices consist of semiconducting materials that directly convert thermal energy into electricity or, oppositely, electricity into a heat flow. These two reciprocal phenomena are known as the Seebeck effect and Peltier effect, respectively, discovered in the early 1800s by Thomas J. Seebeck and Jean Peltier. Today, the thermoelectric effect is used in various day-to-day applications, e.g., refrigerators, heat engines, and heat flow sensors. An exciting and recent application of the Seebeck effect is in the development of energy-harvesting technology. The basic principle of this technology is a number of thermocouples that are electrically connected in series to obtain a reasonable thermoelectric output voltage. The resulting thermoelectric module is a thin film that can be glued to hot surfaces to capture waste heat energy and convert it into electricity.
Electrons have three main properties: mass, charge, and spin. The charge property of electrons is the underlying driving mechanism of all traditional electronics, such as conventional thermoelectric devices. This project aims to investigate a new type of thermoelectric effect that additionally takes into account the spin property of electrons. The effect exists in magnetic materials in contact with heavy metals, in which thermal energies produce spin currents that are further converted into electricity via an effect known as the inverse spin Hall effect. This project will investigate this new spin-based thermoelectric effect in antiferromagnetic materials. By developing new theories, which will be experimentally tested and verified, the project will explore the efficiency of the effect and how it that be applied to improve the heat-to-electricity conversion efficiency of future thermoelectric generators.
The need for smaller, faster, and more efficient devices has put a considerable demand on the thermal management of electronics. In this context, energy-harvesting technology is exciting. The energy-harvesting technology captures the waste heat produced by the electronics and converts it into electricity. Therefore, the technology is expected to be a powerful approach to produce renewable and clean energy and improve the sustainability of electronic infrastructure. Potential applications range from self-powered wireless sensor networks to mobile phones and computers that recycle their own waste heat to improve their overall energy efficiency. The ultimate goal of this project is to take thermoelectric technology to a new level by exploiting the unique spin-based thermoelectric properties of antiferromagnets (AFs). The antiferromagnetic thermoelectric generators are nano-thin heterostructures comprised of layers of AFs and heavy metals (HMs), making them easy to fabricate and attach to various types of surfaces compared to conventional thermoelectric converters based on thermocouples. Potentially, the antiferromagnetic devices can have a figure of merit that is an order of magnitude larger than today's cutting-edge thermoelectric technology, which will make antiferromagnetic thermoelectrics commercially competitive. The project aims to develop a unified theoretical and experimental description of the proposed antiferromagnetic thermoelectric generators and investigate the optimization of the devices. The anticipated application potential of our findings is in developing novel spin-based thermoelectric generators with ultra-high heat-to-electricity conversion efficiencies, which are easily integrable in CMOS devices and wireless sensor networks.