Browsing by Author "Scheller, C. P."

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    Metallic Coulomb blockade thermometry down to 10 mK and below
    (AIP Publishing, 2012) Casparis, L.; Meschke, M.; Maradan, D.; Clark, A. C.; Scheller, C. P.; Schwarzwälder, K. K.; Pekola, Jukka P.; Zumbühl, D. M.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of Science
    We present an improved nuclear refrigerator reaching 0.3 mK, aimed at microkelvin nanoelectronic experiments, and use it to investigate metallic Coulomb blockadethermometers (CBTs) with various resistances R. The high-R devices cool to slightly lower T, consistent with better isolation from the noise environment, and exhibit electron-phonon cooling ∝ T  5 and a residual heat-leak of 40 aW. In contrast, the low-R CBTs display cooling with a clearly weaker T-dependence, deviating from the electron-phonon mechanism. The CBTs agree excellently with the refrigerator temperature above 20 mK and reach a minimum-T of 7.5 ± 0.2 mK.
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    On-and-off chip cooling of a Coulomb blockade thermometer down to 2.8 mK
    (2017-12-18) Palma, M.; Scheller, C. P.; Maradan, D.; Feshchenko, A. V.; Meschke, M.; Zumbühl, D. M.; Department of Applied Physics; Quantum Phenomena and Devices; University of Basel
    Cooling nanoelectronic devices below 10 mK is a great challenge since thermal conductivities become very small, thus creating a pronounced sensitivity to heat leaks. Here, we overcome these difficulties by using adiabatic demagnetization of both the electronic leads and the large metallic islands of a Coulomb blockade thermometer. This reduces the external heat leak through the leads and also provides on-chip refrigeration, together cooling the thermometer down to 2.8 ± 0.1 mK. We present a thermal model which gives a good qualitative account and suggests that the main limitation is heating due to pulse tube vibrations. With better decoupling, temperatures below 1 mK should be within reach, thus opening the door for μK nanoelectronics.