104 research outputs found
On-Chip Cooling by Heating with Superconducting Tunnel Junctions
Heat management and refrigeration are key concepts for nanoscale devices
operating at cryogenic temperatures. The design of an on-chip mesoscopic
refrigerator that works thanks to the input heat is presented, thus realizing a
solid state implementation of the concept of cooling by heating. The system
consists of a circuit featuring a thermoelectric element based on a
ferromagnetic insulator-superconductor tunnel junction (N-FI-S) and a series of
two normal metal-superconductor tunnel junctions (SINIS). The N-FI-S element
converts the incoming heat in a thermovoltage, which is applied to the SINIS,
thereby yielding cooling. The cooler's performance is investigated as a
function of the input heat current for different bath temperatures. We show
that this system can efficiently employ the performance of SINIS refrigeration,
with a substantial cooling of the normal metal island. Its scalability and
simplicity in the design makes it a promising building block for
low-temperature on-chip energy management applications.Comment: 7 pages, 6 figure
Thermopower induced by a supercurrent in superconductor-normal-metal structures
We examine the thermopower Q of a mesoscopic normal-metal (N) wire in contact
to superconducting (S) segments and show that even with electron-hole symmetry,
Q may become finite due to the presence of supercurrents. Moreover, we show how
the dominant part of Q can be directly related to the equilibrium supercurrents
in the structure. In general, a finite thermopower appears both between the N
reservoirs and the superconductors, and between the N reservoirs themselves.
The latter, however, strongly depends on the geometrical symmetry of the
structure.Comment: 4 pages, 4 figures; text compacted and material adde
Electron-phonon coupling in single walled carbon nanotubes determined by shot noise
We have measured shot noise in metallic single-walled carbon nanotubes of
length L=1 m and have found strong suppression of noise with increasing
voltage. We conclude that the coupling of electron and phonon baths at
temperatures and is described at intermediate bias (20 mV
\vv 200 mV) by heat flow equation
where W/mK due to electron interaction with
acoustic phonons, while at higher voltages optical phonon - electron
interaction leads to where with optical phonons energy and
W/m.Comment: 9 pages, 3 figure
0- phase-controllable Josephson junction
Two superconductors coupled by a weak link support an equilibrium Josephson
electrical current which depends on the phase difference between the
superconducting condensates [1]. Yet, when a temperature gradient is imposed
across the junction, the Josephson effect manifests itself through a coherent
component of the heat current that flows oppositely to the thermal gradient for
[2-4]. The direction of both the Josephson charge and heat
currents can be inverted by adding a shift to . In the static
electrical case, this effect was obtained in a few systems, e.g. via a
ferromagnetic coupling [5,6] or a non-equilibrium distribution in the weak link
[7]. These structures opened new possibilities for superconducting quantum
logic [6,8] and ultralow power superconducting computers [9]. Here, we report
the first experimental realization of a thermal Josephson junction whose phase
bias can be controlled from to . This is obtained thanks to a
superconducting quantum interferometer that allows to fully control the
direction of the coherent energy transfer through the junction [10]. This
possibility, joined to the completely superconducting nature of our system,
provides temperature modulations with unprecedented amplitude of 100 mK
and transfer coefficients exceeding 1 K per flux quantum at 25 mK. Then, this
quantum structure represents a fundamental step towards the realization of
caloritronic logic components, such as thermal transistors, switches and memory
devices [10,11]. These elements, combined with heat interferometers [3,4,12]
and diodes [13,14], would complete the thermal conversion of the most important
phase-coherent electronic devices and benefit cryogenic microcircuits requiring
energy management, such as quantum computing architectures and radiation
sensors.Comment: 10 pages, 9 color figure
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