Researchers at Aalto University, Finland and the University of Tokyo have succeeded for the first time in experimentally measuring a probability distribution for entropy production of electrons. Entropy production means an increase in disorder when electrons are moved individually between two microscopic conductors of differing temperatures.
The researchers also showed that a connection prevails between two definitions of entropy that have been used. The result is significant for the design of future nanoelectronic devices. The study was published recently in the scientific journal Nature Physics.
Similar experiments have been conducted before, but this is the first time the researchers have used conductors at different temperatures to measure the entropy production of electrons.
'Entropy production is defined either by the time when the shift takes place or by the heat that moves from one conductor to another. In the study we measured electronic entropy production according to both definitions. The change in entropy in an individual measurement is random: the distribution for production is acquired by repeating the process about 100,000 times, for instance. Both distributions follow the so-called fluctuation relation', says doctoral candidate Jonne Koski from Aalto University.
Fluctuation relations are relatively new discoveries of thermodynamics and statistical physics. When the probability to produce a certain amount of disorder of electrons, or entropy, is precisely known, the fluctuation relation is an equation, which gives a probability for the decrease in the amount of entropy. Therefore, the degree of disorder of electrons can decline when the nanostructures are examined for short periods of time.
'Entropy production leads to overheating in the nanostructures, which is why it is important to get more information on their heat transmission properties', says Professor Jukka Pekola from Aalto University.
Link to the Nature Physics publication: http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys2711.html
Additional information:
Professor Jukka Pekola
jukka.pekola@aalto.fi
Tel. +358 50 344 2697
Doctoral Candidate Jonne Koski
jonne.koski@aalto.fi
Tel. +358 44 335 9000
Aalto University School of Science
O.V. Lounasmaa Laboratory - low temperature laboratory
The research group's website: http://ltl.tkk.fi/PICO/wordpress/?page_id=349
Aalto University, Finland is a new multidisciplinary science and art community in the fields of science, economics, and art and design. The University is founded on Finnish strengths, and its goal is to develop as a unique entity to become one of the world's top universities. Aalto University's cornerstones are its strengths in education and research. At the new University, there are 20,000 basic degree and graduate students as well as a staff of 5,000 of which 370 are professors.
Journal
Nature Physics