Magnetic Effect: Groundbreaking Discovery for Low-Temperature Thermoelectric Cooling
Researchers at the Max Planck Institute for Chemical Physics of Solids, in collaboration with Chongqing University and the Max Planck Institute of Microstructure Physics, have achieved a breakthrough in topological thermoelectrics. In their study, published in “Nature Materials”, they demonstrate a groundbreaking development in thermoelectrics: By applying a weak magnetic field, the cooling performance of topological materials at low temperatures can be significantly improved. It marks a significant advance in magneto-thermoelectrics, which can be a cost-effective and energy-efficient alternative to traditional cooling methods.
Revived Interest in Thermoelectric Materials
In recent years, thanks to worldwide research activities in the development and research of topological materials and the associated theory of topological band structures, interest in thermoelectric materials has increased again. Various approaches and ideas have been pursued. One of the ideas of the international team of researchers from the Max Planck Institute for Chemical Physics of Solids, Chongqing University and the Max Planck Institute of Microstructure Physics proved to be extremely successful: they were able to achieve a remarkably high “figure of merit” zT value of 1.7 ± 0.2 at 180 Kelvin under the influence of a low magnetic field of only 0.7 Tesla. To do this, they used a single-crystal material made of bismuth and antimony, the topological insulator Bi88Sb12. This observation is all the more remarkable because zT is almost three times higher than without a magnetic field. In addition, this “magnetic” zT value exceeds that of all known thermoelectric materials for low temperatures.
Prospects about High Magnetic-Thermoelectric Performance
The crucial step to realize this high magnetic-thermoelectric performance is to grow high-quality Bi1–xSbx single crystals. This represents a major challenge. Bi and Sb are completely miscible, but at the same time there is a strong tendency towards phase segregation, i.e. demixing and formation of regions of different composition. The researchers therefore used the zone melting method. In-house equipment was able to produce high-quality single crystals with a low charge carrier density of around 1017 cm-3 and a high mobility of over 4 × 105 cm²V-1s-1 at 80 K. The high charge carrier mobility together with the unique band dispersion of Bi1–xSbx is crucial for the exceptionally high zT value and the high magnetic-thermoelectric performance of Bi88Sb12.
Theoretical modeling shows that the Dirac band with its linear band dispersion plays a key role in a large magnetic Seebeck effect, which is further enhanced by the Zeeman splitting due to the large Landé g-factor. Many topological materials exhibit similar properties such as a linear Dirac band dispersion and a very small effective mass (as well as a large g-factor). It is therefore expected that high magneto-thermoelectric performance can also be achieved with other novel topological materials. “We believe that a deeper understanding of the magneto-thermoelectric properties of Bi1–xSbx will facilitate the development of topological thermoelectrics for low-temperature cooling applications,” say the two lead authors Yu Pan and Claudia Felser.
The Substantial Role of Small Magnetic Fields in Thermoelectric Applications
The results of the study are therefore based on the idea of using small magnetic fields to significantly increase the performance in thermoelectric applications. It is particularly noteworthy that high zT values can already be achieved in relatively low magnetic fields. Since such fields can be generated using conventional permanent magnets, this opens up a new perspective for cost-effective and efficient thermoelectric cooling devices. The observations also motivate further studies to explore other topological materials with similar properties. There are already possibilities of how the thermoelectric performance in these substances could be shifted to even higher values.
Original Source: https://www.cpfs.mpg.de/3698623/20250106a
Expert Contacts
Claudia Felser
Director
Email ID: Claudia.Felser@cpfs.mpg.de
Yu Pan
Chongqing University
Chongqing
People’s Republic of China
Email ID: Yu.Pan@cpfs.mpg.de
Original Publications
Yu Pan, Bin He, Xiaolong Feng, Fan Li, Dong Chen, Ulrich Burkhardt, Claudia Felser
Journal: Nature Materials
Article Title: A magneto-thermoelectric with a high figure of merit in topological insulator Bi88Sb12
Article Publication Date: 03 January 2025
DOI: https://doi.org/10.1038/s41563-024-02059-9
Yu Pan, Claudia Felser
Journal: Nature Materials
Article Title: A weak magnetic field enhances the thermoelectric performance of topological materials
Article Publication Date: 03 January 2025
DOI: https://doi.org/10.1038/s41563-024-02070-0
Media Contact
Liane Schröder
Public Relations
Email ID: pr@cpfs.mpg.de
Phone Number: +49 351 4646-3602
Source: IDW
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