Browsing by Author "Savin, Alexander M."

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Heat Transistor: Demonstration of Gate-Controlled Electronic Refrigeration
(2007) Saira, Olli-Pentti; Meschke, Matthias; Giazotto, Francesco; Savin, Alexander M.; Möttönen, Mikko; Pekola, Jukka P.
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We present experiments on a superconductor–normal-metal electron refrigerator in a regime where single-electron charging effects are significant. The system functions as a heat transistor; i.e., the heat flux out from the normal-metal island can be controlled with a gate voltage. A theoretical model developed within the framework of single-electron tunneling provides a full quantitative agreement with the experiment. This work serves as the first experimental observation of Coulombic control of heat transfer and, in particular, of refrigeration in a mesoscopic system.
Opportunities for mesoscopics in thermometry and refrigeration: Physics and applications
(2006) Giazotto, Francesco; Heikkilä, Tero T.; Luukanen, Arttu; Savin, Alexander M.; Pekola, Jukka P.
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This review presents an overview of the thermal properties of mesoscopic structures. The discussion is based on the concept of electron energy distribution, and, in particular, on controlling and probing it. The temperature of an electron gas is determined by this distribution: refrigeration is equivalent to narrowing it, and thermometry is probing its convolution with a function characterizing the measuring device. Temperature exists, strictly speaking, only in quasiequilibrium in which the distribution follows the Fermi-Dirac form. Interesting nonequilibrium deviations can occur due to slow relaxation rates of the electrons, e.g., among themselves or with lattice phonons. Observation and applications of nonequilibrium phenomena are also discussed. The focus in this paper is at low temperatures, primarily below 4K, where physical phenomena on mesoscopic scales and hybrid combinations of various types of materials, e.g., superconductors, normal metals, insulators, and doped semiconductors, open up a rich variety of device concepts. This review starts with an introduction to theoretical concepts and experimental results on thermal properties of mesoscopic structures. Then thermometry and refrigeration are examined with an emphasis on experiments. An immediate application of solid-state refrigeration and thermometry is in ultrasensitive radiation detection, which is discussed in depth. This review concludes with a summary of pertinent fabrication methods of presented devices.