title: Metallic Coulomb blockade thermometry down to 10 mK and below.
abstract: We present an improved nuclear refrigerator reaching 0.3 mK, aimed at microkelvin nanoelectronic experiments, and use it to investigate metallic Coulomb blockade thermometers (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 [proportional] 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.
authors.affiliation: Department of Physics, University of Basel, CH-4056 Basel, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Casparis
authors.forename: M
authors.initials: M
authors.lastname: Meschke
authors.forename: D
authors.initials: D
authors.lastname: Maradan
authors.forename: A C
authors.initials: AC
authors.lastname: Clark
authors.forename: C P
authors.initials: CP
authors.lastname: Scheller
authors.forename: K K
authors.initials: KK
authors.lastname: Schwarzwälder
authors.forename: J P
authors.initials: JP
authors.lastname: Pekola
authors.forename: D M
authors.initials: DM
authors.lastname: Zumbühl