The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Temperature Fluctuations and Heat Transport in Nanoelectronics

Matti Laakso

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the School of Science for public examination and debate in Auditorium T2 at the Aalto University School of Science (Espoo, Finland) on the 25th of May 2012 at 12 noon.

Overview in PDF format (ISBN 978-952-60-4631-0)   [3638 KB]
Dissertation is also available in print (ISBN 978-952-60-4630-3)


In metallic structures at very low temperatures heat and energy are carried mostly by electrons. When these structures are small, with dimensions of the order of nanometers, many kinds of quantum phenomena become significant. The combination of heat transport with these effects, with a special focus on the random fluctuations of temperature in these systems, is the topic of this Dissertation.

Using quantum transport theory, we have studied the flow of heat and charge in some prototypical nanoelectronic systems, e.g., single-electron transistor and superconductor–normal metal tunnel structure. We have devised a powerful theoretical method for the calculation of probability distributions of fluctuating quantities, especially temperature, and used it to find cases where the statistics of these fluctuations becomes non-Gaussian. We have also shown how the fluctuations of temperature affect the fluctuations of the electric current. In some cases the temperature-fluctuation induced current noise can be orders of magnitude larger than the intrinsic shot noise of the system. We also address the possibility to detect these fluctuations by monitoring the induced current noise.

This thesis consists of an overview and of the following 6 publications:

  1. M. A. Laakso, T. T. Heikkilä, and Yuli V. Nazarov. Fully Overheated Single-Electron Transistor. Physical Review Letters, Volume 104, Number 19, 196805, May 2010. © 2010 American Physical Society (APS). By permission.
  2. M. A. Laakso, T. T. Heikkilä, and Yuli V. Nazarov. Giant current fluctuations in an overheated single-electron transistor. Physical Review B, Volume 82, Number 20, 205316, November 2010. © 2010 American Physical Society (APS). By permission.
  3. M. A. Laakso, T. T. Heikkilä, and Yuli V. Nazarov. Manifestly non-Gaussian fluctuations in superconductor-normal metal tunnel nanostructures. Physical Review Letters, Volume 108, Number 6, 067002, February 2012. © 2012 American Physical Society (APS). By permission.
  4. M. A. Laakso, T. T. Heikkilä, and Yuli V. Nazarov. Theory of temperature fluctuation statistics in superconductor-normal metal tunnel structures. Physical Review B, April 2012. © 2012 American Physical Society (APS). By permission.
  5. J. Voutilainen, M. A. Laakso, and T. T. Heikkilä. Physics of proximity Josephson sensor. Journal of Applied Physics, Volume 107, Number 6, 064508, March 2010. © 2010 American Institute of Physics (AIP). By permission.
  6. M. A. Laakso, P. Virtanen, F. Giazotto, and T. T. Heikkilä. Nonequilibrium characteristics in all-superconducting tunnel structures. Physical Review B, Volume 75, Number 9, 094507, March 2007. © 2007 American Physical Society (APS). By permission.

Keywords: temperature fluctuations, heat transport, noise

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© 2012 Aalto University

Last update 2012-10-31