Assistant Professor Yo Machida and Professor Koichi Izawa of the Graduate School of Science and Engineering, Tokyo Institute of Technology, et al. We have discovered a huge thermoelectric effect that is 2 times that of materials.This research is the result of collaboration with researchers at Ewha Womans University (Korea) and Paris Higher Physical Chemistry School (France).

 The phenomenon in which an electromotive force is generated when a temperature difference is applied to both ends of a substance is called the Seebeck effect, and the magnitude of this effect is expressed by the Seebeck coefficient S [voltage generated per 1K (absolute temperature) temperature difference].The Seebeck effect is attracting attention as a technology that can convert waste heat energy into electrical energy (thermoelectric conversion), and currently, high-efficiency thermoelectric conversion materials are being energetically developed, centering on semiconductors with a large Seebeck coefficient.

 The (TMTSF) 2PF6, which was the subject of research by the same research group, changes from metal to semiconductor at minus 261.15 ° C (absolute temperature 12K) with temperature changes, and the repulsive force (Couron interaction) acting between two electrons is present. It is a strongly strongly correlated electron-based organic compound.This time, when the Seebeck coefficient of the same substance is measured precisely to extremely low temperature, the same coefficient | S | shows a remarkable increase even at extremely low temperature where electricity is very difficult to flow, and is 2 at around 273.05 ° C (absolute temperature 0.1K). We have found that it reaches a huge value of mV / K.This value is 40 to 10 times higher than that of thermoelectric conversion materials such as silicon, germanium, or bismuth tellurium (BiTe).

 The result of this research is that it is a novel phenomenon with a new mechanism that overturns the conventional theoretical prediction that the thermoelectric effect of semiconductors disappears at low temperatures.It is expected that this discovery will provide new guidelines for the development of substances that exhibit a large thermoelectric effect in the future.

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