Featured Research

from universities, journals, and other organizations

Large thermoelectric power from a combination of magnets and superconductors

Date:
February 7, 2014
Source:
Suomen Akatemia (Academy of Finland)
Summary:
Thermoelectric devices can cool materials by passing currents, or convert temperature differences into electric power. However, especially metallic structures have a very poor thermoelectric performance, and therefore most thermoelectrics are made of semiconductors. Now researchers have shown how a proper combination of magnetic metals and superconductors could allow reaching very strong thermoelectric conversion efficiency.

According to the newly published research, a very large thermoelectric effect can be created in a structure combining a ferromagnet (F) to a thin superconductor film (S) via an insulator (I), and where the superconductor is in the presence of a spin-splitting field due to the presence of a ferromagnetic insulator (FI) or a magnetic field (B).
Credit: Courtesy Academy of Finland

Thermoelectric devices can cool materials by passing currents, or convert temperature differences into electric power. However, especially metallic structures have a very poor thermoelectric performance, and therefore most thermoelectrics are made of semiconductors. Now a group of researchers from the University of Jyväskylä, Aalto University (Finland), San Sebastian (Spain) and Oldenburg University (Germany) have shown how a proper combination of magnetic metals and superconductors could allow reaching very strong thermoelectric conversion efficiency.

The electronic structure of semiconductors and superconductors looks superficially similar, because both contain an "energy gap," a region of energies forbidden for the electrons. The difference between the two is that doping semiconductors allows moving this energy gap with respect to the average electron energy. This is in contrast to superconductors, where the energy gap is symmetric with respect to positive and negative energies, and therefore the thermoelectric effect from positive energy electrons cancels the effect from the negative energy electrons. In the work published yesterday Heikkilä and the international research group showed how this symmetry can be broken by the presence of an extra magnetic field, and driving the electric current through a magnetic contact. As a result, the system exhibits a very large thermoelectric effect.

Because conventional superconductors require temperatures of the order of a few Kelvin, this mechanism cannot be used directly in consumer devices such as portable coolers or waste heat converters. However, it could be used in accurate signal detection, or a similar mechanism could be applied in semiconductors to improve their thermoelectric performance.

Converting heat to electricity or vice versa

Thermoelectric effects were found already in the 1830's, when the Estonian scientist Thomas Johann Seebeck observed a voltage caused by a temperature difference, and a French physicist Jean Charles Athanase Peltier discovered the reciprocal effect, capable of converting electric current to temperature differences. These phenomena have been used in many applications ranging from thermometry to cooling car seats and as power sources for space missions. The efficiency of such devices is typically quite low. If it could be improved, the thermoelectric conversion would be immediately taken into use to convert the waste heat in industrial processes or for example car engines into useful electricity.

Some metals turn at low temperatures to superconductors, losing entirely their electrical resistance. It was long believed that superconductors exhibit no thermoelectric effects. However, in his Nobel lecture 2003, Vitaly Ginsburg described the topic as poorly understood. The new research brings insight into this question and allows studying phenomena in more complicated hybrid structures.


Story Source:

The above story is based on materials provided by Suomen Akatemia (Academy of Finland). Note: Materials may be edited for content and length.


Journal Reference:

  1. A. Ozaeta, P. Virtanen, F. S. Bergeret, ja T. T. Heikkil. Predicted Very Large Thermoelectric Effect in Ferromagnet-Superconductor Junctions in the Presence of a Spin-Splitting Magnetic Field. Phys. Rev. Lett., 2014 DOI: 10.1103/PhysRevLett.112.057001

Cite This Page:

Suomen Akatemia (Academy of Finland). "Large thermoelectric power from a combination of magnets and superconductors." ScienceDaily. ScienceDaily, 7 February 2014. <www.sciencedaily.com/releases/2014/02/140207083738.htm>.
Suomen Akatemia (Academy of Finland). (2014, February 7). Large thermoelectric power from a combination of magnets and superconductors. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2014/02/140207083738.htm
Suomen Akatemia (Academy of Finland). "Large thermoelectric power from a combination of magnets and superconductors." ScienceDaily. www.sciencedaily.com/releases/2014/02/140207083738.htm (accessed September 19, 2014).

Share This



More Matter & Energy News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

MIT BioSuit A New Take On Traditional Spacesuits

MIT BioSuit A New Take On Traditional Spacesuits

Newsy (Sep. 19, 2014) — The MIT BioSuit could be an alternative to big, bulky traditional spacesuits, but the concept needs some work. Video provided by Newsy
Powered by NewsLook.com
Virtual Reality Headsets Unveiled at Tokyo Game Show

Virtual Reality Headsets Unveiled at Tokyo Game Show

AFP (Sep. 18, 2014) — Several companies unveiled virtual reality headsets at the Tokyo Game Show, Asia's largest digital entertainment exhibition. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Apple's iOS8 Includes New 'Killswitch' To Curb Theft

Apple's iOS8 Includes New 'Killswitch' To Curb Theft

Newsy (Sep. 18, 2014) — Apple's new operating system, iOS 8, comes with Apple's killswitch feature already activated, unlike all the models before it. Video provided by Newsy
Powered by NewsLook.com
Stocks Hit All-Time High as Fed Holds Steady

Stocks Hit All-Time High as Fed Holds Steady

AP (Sep. 17, 2014) — The Federal Reserve signaled Wednesday that it plans to keep a key interest rate at a record low because a broad range of U.S. economic measures remain subpar. Stocks hit an all-time high on the news. (Sept. 17) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins