Prance, J. R. and Bradley, D. I. and George, R. E. and Haley, R. P. and Pashkin, Yu A. and Sarsby, M. and Penttilä, J. and Roschier, L. and Gunnarsson, D. and Heikkinen, H. and Prunnila, M. (2015) Nanoelectronic thermometers optimised for sub-10 millikelvin operation. arxiv.org.
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Abstract
We report the cooling of electrons in nanoelectronic Coulomb blockade thermometers below 4 mK. Above 7 mK the devices are in good thermal contact with the environment, well isolated from electrical noise, and not susceptible to self-heating. This is attributed to an optimised design that incorporates cooling fins with a high electron-phonon coupling and on-chip electronic filters, combined with a low-noise electronic measurement setup. Below 7 mK the electron temperature is seen to diverge from the ambient temperature. By immersing a Coulomb Blockade Thermometer in the 3He/4He refrigerant of a dilution refrigerator, we measure a lowest electron temperature of 3.7 mK.