Browsing by Author "Maradan, D."
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Item 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 ScienceWe 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.Item 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 BaselCooling 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.Item Tunnel junction thermometry down to millikelvin temperatures(2015-09-03) Feshchenko, Anna; Casparis, L.; Khaymovich, Ivan; Maradan, D.; Saira, Olli-Pentti; Palma, M.; Meschke, M.; Pekola, Jukka; Zumbühl, D.M.; Department of Applied PhysicsWe present a simple on-chip electronic thermometer with the potential to operate down to 1 mK. It is based on transport through a single normal-metal–superconductor tunnel junction with rapidly widening leads. The current through the junction is determined by the temperature of the normal electrode that is efficiently thermalized to the phonon bath, and it is virtually insensitive to the temperature of the superconductor, even when the latter is relatively far from equilibrium. We demonstrate here the operation of the device down to 7 mK and present a systematic thermal analysis.