6 research outputs found
Calorimetric readout of a superconducting proximity-effect thermometer
A proximity-effect thermometer measures the temperature dependent critical
supercurrent in a long superconductor - normal metal - superconductor (SNS)
Josephson junction. Typically, the transition from the superconducting to the
normal state is detected by monitoring the appearance of a voltage across the
junction. We describe a new approach to detect the transition based on the
temperature increase in the resistive state due to Joule heating. Our method
increases the sensitivity and is especially applicable for temperatures below
about 300 mK.Comment: 10 pages, 5 figures. To appear in the proceedings of the Conference
on Micro- and Nanocryogenics (LT25 satellite) organized in Espoo, Finland
(2008
Electronic and thermal sequential transport in metallic and superconducting two-junction arrays
The description of transport phenomena in devices consisting of arrays of
tunnel junctions, and the experimental confirmation of these predictions is one
of the great successes of mesoscopic physics. The aim of this paper is to give
a self-consistent review of sequential transport processes in such devices,
based on the so-called "orthodox" model. We calculate numerically the
current-voltage (I-V) curves, the conductance versus bias voltage (G-V) curves,
and the associated thermal transport in symmetric and asymmetric two-junction
arrays such as Coulomb-blockade thermometers (CBTs),
superconducting-insulator-normal-insulator-superconducting (SINIS) structures,
and superconducting single-electron transistors (SETs). We investigate the
behavior of these systems at the singularity-matching bias points, the
dependence of microrefrigeration effects on the charging energy of the island,
and the effect of a finite superconducting gap on Coulomb-blockade thermometry.Comment: 23 pages, 12 figures; Berlin (ISBN: 978-3-642-12069-5
Nonequilibrium electron cooling by NIS tunnel junctions
We discuss the theoretical framework to describe quasiparticle electric and
heat currents in NIS tunnel junctions in the dirty limit. The approach is based
on quasiclassical Keldysh-Usadel equations. We apply this theory to diffusive
NIS'S tunnel junctions. Here N and S are respectively normal metal and
superconductor reservoirs, I is an insulator layer and S' is a nonequilibrium
superconducting lead. We calculate the quasiparticle electric and heat currents
in such structures and consider the effect of inelastic relaxation in the S'
lead. We find that in the absence of strong relaxation the electric current and
the cooling power for voltages are suppressed. The value of this
suppression scales with the diffusive transparency parameter. We ascribe this
suppression to the effect of backtunneling of nonequilibrium quasiparticles
into the normal metal.Comment: 12 pages, 6 figures, proceedings, to be published in JLT