Practical electron-tunneling refrigerator

Clark, Anthony C.; Williams, A. J.; Ruggiero, S. T.; Berg, M.L. van den; Ullom, Joel N.

doi:10.1063/1.1644326

Cited by 59 publications

(49 citation statements)

References 8 publications

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“…In this configuration, a reduction of the electron temperature from 300 to about 100 mK was obtained. Later on, other experimental evidence of electron cooling in SINIS metallic structures was reported ͑Fisher et Leoni et al, 1999Leoni et al, , 2003Vystavkin et al, 1999;Arutyunov et al, 2000;Luukanen et al, 2000;Pekola, Anghel, et al, 2000;Tarasov et al, 2003;Clark et al, 2004;Pekola, Heikkilä, et al, 2004͒. In these experiments NIS junc- FIG. 26.…”

Section: "Si…nis Structuresmentioning

confidence: 88%

Opportunities for mesoscopics in thermometry and refrigeration: Physics and applications

et al. 2006

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This review presents an overview of the thermal properties of mesoscopic structures. The discussion is based on the concept of electron energy distribution, and, in particular, on controlling and probing it. The temperature of an electron gas is determined by this distribution: refrigeration is equivalent to narrowing it, and thermometry is probing its convolution with a function characterizing the measuring device. Temperature exists, strictly speaking, only in quasiequilibrium in which the distribution follows the Fermi-Dirac form. Interesting nonequilibrium deviations can occur due to slow relaxation rates of the electrons, e.g., among themselves or with lattice phonons. Observation and applications of nonequilibrium phenomena are also discussed. The focus in this paper is at low temperatures, primarily below 4 K, where physical phenomena on mesoscopic scales and hybrid combinations of various types of materials, e.g., superconductors, normal metals, insulators, and doped semiconductors, open up a rich variety of device concepts. This review starts with an introduction to theoretical concepts and experimental results on thermal properties of mesoscopic structures. Then thermometry and refrigeration are examined with an emphasis on experiments. An immediate application of solid-state refrigeration and thermometry is in ultrasensitive radiation detection, which is discussed in depth. This review concludes with a summary of pertinent fabrication methods of presented devices.

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Section: "Si…nis Structuresmentioning

confidence: 88%

Opportunities for mesoscopics in thermometry and refrigeration: Physics and applications

et al. 2006

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“…The effect can be made to be more pronounced in a symmetric double-junction SINIS structure with a small N island contacted to S leads via two NIS junctions, 15 allowing to construct practical solid-state refrigerators for cooling thin-film detectors to temperatures close to 100 mK. 16,17 The performance of actual devices depends crucially on the relaxation of the QPs that are injected into the S electrode, as the superconductor overheating diminishes the cooling power at a NIS junction because of enhanced QP backtunneling. The excess QP density close to the junction can be diminished by ©2011 American Physical Society fabricating very thick S electrodes, 16 or covering them partially by a layer of normal metal that acts as a QP trap.…”

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confidence: 99%

“…16,17 The performance of actual devices depends crucially on the relaxation of the QPs that are injected into the S electrode, as the superconductor overheating diminishes the cooling power at a NIS junction because of enhanced QP backtunneling. The excess QP density close to the junction can be diminished by ©2011 American Physical Society fabricating very thick S electrodes, 16 or covering them partially by a layer of normal metal that acts as a QP trap. [18][19][20] The QP population is typically modeled in terms of a diffusion equation, describing their recombination retarded by phonon retrapping, and other loss mechanisms.…”

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confidence: 99%

Magnetic-field-induced stabilization of nonequilibrium superconductivity in a normal-metal/insulator/superconductor junction

Peltonen¹,

Muhonen

Meschke³

et al. 2011

Phys. Rev. B

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A small magnetic field is found to enhance relaxation processes in a superconductor, thus stabilizing superconductivity in nonequilibrium conditions. In a normal-metal (N)/insulator/superconductor (S) tunnel junction, applying a field of the order of 100 μT leads to significantly improved cooling of the N island by quasiparticle (QP) tunneling. These findings are attributed to faster QP relaxation within the S electrodes as a result of enhanced QP drain through regions with a locally suppressed energy gap due to magnetic vortices in the S leads at some distance from the junction. Introduction. In this Rapid Communication, we report an observation that appears counterintuitive at first: A small magnetic field is found to stabilize superconductivity under quasiparticle (QP) injection. In our experiment, the cooling power of normal-metal (N)/insulator (I)/superconductor (S) tunnel structures is enhanced in perpendicular magnetic fields B ⊥ 100 μT = 1 G. A measured maximum temperature drop δT relative to a starting bath temperature T 0 = 285 mK exhibiting this behavior is shown in Fig. 1(a). The improvement is unexpected, as in general the effect of a magnetic field is to suppress superconductivity. Electronic cooling in NIS junctions in the presence of magnetic fields in both perpendicular and parallel orientations has been studied before, 1 but only in higher fields where the cooling power was already reduced due to a diminishing superconducting energy gap . On the other hand, the creation of magnetic vortices 2 has been shown to enhance QP relaxation in superconducting aluminum, as the QPs become trapped and thermalize in the regions of a reduced energy gap. 3 Here we demonstrate that the additional relaxation channel due to an enhanced QP drain through regions occupied by magnetic vortices enhances the superconducting performance of S leads and improves the electronic cooling in NIS junctions. This can be of relevance in superconducting qubits, 4-7 resonators, 8 and in hybrid SINIS turnstiles 9 in reducing the effects from nonequilibrium and residual QPs arising due to drive and microwave radiation from the environment. Moreover, improved relaxation caused by vortex creation in the S leads can partially explain the "reentrant superconductivity" observed in Zn and Al nanowires. 10,11 In the present case, as sketched in Fig. 1(a), vortex formation in the S electrodes away from the NIS junction improves relaxation of the injected QPs and leads to enhanced cooling of the N island. In higher fields, vortices move closer to the junction, deteriorating the cooling power.In a NIS junction, acts as an energy filter for the tunneling QP. [12][13][14][15] At low temperatures k B T and for bias voltages eV across the junction, the electrons in the N electrode cool considerably below the phonon temperature by hot QP extraction. The effect can be made to be more pronounced in a symmetric double-junction SINIS structure with a small N

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“…10 Although it is possible to have both NIN and NIS Al-based junctions in a single circuit by controlling the thicknesses and thus the critical fields of Al layers, 11 in some applications external fields cannot be tolerated. Another approach is to dope Al with, e.g., manganese impurities to control or diminish the T C while retaining the BCS density of states 6,12 but the junction quality could be compromised, 13 and it is undesirable to have both manganese-doped and pure superconducting materials in the same evaporator due to the risk of contamination. Also the use of inverse proximity effect arising in a normal metal-superconductor ͑NS͒ bilayer is a widely used technique for modifying the superconductor T C : 14,15 the normal metal gains a superconducting character while the superconductor gains normal metal features at a short distance from the interface.…”

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confidence: 99%

“…[3][4][5][6] A standard material for yielding high-quality junctions is aluminum due to rapid oxidation of its surface into a thin and stable layer of insulating aluminum oxide ͑AlO x ͒ under oxygen exposure. Aluminum is superconducting below the critical temperature T C = 1.2 K in bulk and up to 2.7 K in thin films.…”

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confidence: 99%

Laterally proximized aluminum tunnel junctions

Koski

Peltonen

Meschke

et al. 2011

Applied Physics Letters

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This letter presents experiments on junctions fabricated by a new technique that enables the use of high quality aluminum oxide tunnel barriers with normal metal electrodes at low temperatures. Inverse proximity effect is applied to diminish the superconductivity of an aluminum dot through a clean lateral connection to a normal metal electrode. To demonstrate the effectiveness of this method, fully normal-state single electron transistors (SET) and normal metal-insulator-superconductor (NIS) junctions applying proximized Al junctions were fabricated. The transport characteristics of the junctions were similar to those obtained from standard theoretical models of regular SETs and NIS junctions

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Practical electron-tunneling refrigerator

Cited by 59 publications

References 8 publications

Opportunities for mesoscopics in thermometry and refrigeration: Physics and applications

Opportunities for mesoscopics in thermometry and refrigeration: Physics and applications

Magnetic-field-induced stabilization of nonequilibrium superconductivity in a normal-metal/insulator/superconductor junction

Laterally proximized aluminum tunnel junctions

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