Date: 2018-10-09
Time: 15:00
Venue: M234
Speaker: Joseph P. Heremans,  Ohio Eminent Scholar
               The Ohio State University, Departments of Mechanical and Aerospace Engineering

报告人简介： Heremans is an Ohio Eminent Scholar and Professor in the Mechanical and Aerospace Engineering Department at the Ohio State University, with appointments in the Materials Science and Engineering Department and the Department of Physics. He is a member of the National Academy of Engineering, and a fellow of AAAS and the American Physical Society. He joined OSU after a 21 year career in the automotive industry at the General Motors Research Laboratories, where he was the section manager for Semiconductor Physics, and at the Delphi Research Laboratories. His research interests focus on energy conservation and recovery, and lie at the intersection between experimental condensed matter physics and thermodynamics. In the last decade, he worked on the transport of heat, charge, and magnetization in solids.

报告摘要:

Solid-state heat conversion provides practical cooling at low power levels and has the potential to recover waste heat at power levels below 1kW. The year 2008 saw the birth of a new field, spin caloritronics, that studies the generation of spin currents by temperature gradients. The first effect in this field, the spin Seebeck effect (SSE), opens a new path to solid-state energy conversion: the concepts of thermal spin transport add new approaches beyond classical thermoelectrics. This talk will explain what the SSE is. Thermally-driven spin physics can be further integrated inside bulk ferromagnetic (FM) or antiferromagnetic (AFM) conductors as magnon-drag. Both SSE and magnon drag extend beyond the magnetically ordered phase of FMs and AFMs into the paramagnetic (PM) regime. Under specific circumstances, short-range, short-lived thermally-driven local fluctuations of the magnetization in PMs, paramagnons, can also drag electrons. We show how this new spin physics gives rise to a thermoelectric figure of merit ZT>1 in the PM regime of the AFM semiconductor MnTe at temperatures three times higher its ordering temperature. This is the first example in which a spin-based effect is much more energetic than the equivalent charge-based effect, the diffusion thermopower.

联系人：王玉鹏   研究员（8264 9345）

             赵怀周   副研究员（8264 8119）