Are “Pinholes” the Cause of Excess Current in Superconducting Tunnel Junctions? A Study of Andreev Current in Highly Resistive Junctions

Greibe, Tine; Stenberg, Markku P. V.; Wilson, Christopher; Bauch, Thilo; Shumeiko, Vitaly; Delsing, Per

doi:10.1103/physrevlett.106.097001

Cited by 48 publications

(54 citation statements)

References 33 publications

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“…3(b) indicates 3 pA, which we have chosen as a biasing current for the temperature probe. This value is in the temperature sensitive region, not influenced by the Andreev current leakage [30][31][32] that appears as a constant slope at low bias values in Fig. 3(b).…”

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confidence: 90%

Experimental realization of a Coulomb blockade refrigerator

2014

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We present an experimental realization of a Coulomb blockade refrigerator (CBR) based on a single-electron transistor (SET). In the present structure, the SET island is interrupted by a superconducting inclusion to permit charge transport while preventing heat flow. At certain values of the bias and gate voltages, the current through the SET cools one of the junctions. The measurements follow the theoretical model down to ∼80 mK, which was the base temperature of the current measurements. The observed cooling increases rapidly with decreasing temperature, in agreement with the theory, reaching about a 15 mK drop at the base temperature. The CBR appears as a promising electronic cooler at temperatures well below 100 mK.

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confidence: 90%

Experimental realization of a Coulomb blockade refrigerator

2014

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“…Structural defects at the interface [3,5], roughness of the metal substrate [4,10,11] and nonuniformity of the oxide thickness [3,7,8] are anticipated to be the critical factors, which may deteriorate the functionality of the oxide as a barrier. However, characterization of this impact is in its early stage and hence still uncertain.…”

Section: Introductionmentioning

confidence: 99%

Structural details of Al/Al2O3 junctions and their role in the formation of electron tunnel barriers

2018

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We present a computational study of the adhesive and structural properties of the Al/Al 2 O 3 interfaces as building blocks of the metal-insulator-metal (MIM) tunnel devices, where electron transport is accomplished via tunneling mechanism through the sandwiched insulating barrier. The main goal of this paper is to understand, on the atomic scale, the role of the geometrical details in the formation of the tunnel barrier profiles. Initially, we concentrate on the adhesive properties of the interfaces. To provide reliable results, we carefully assess the accuracy of the traditional methods used to examine Al/Al 2 O 3 systems. These are the most widely employed exchangecorrelation functionals-local-density approximation and two different generalized gradient approximations; the universal binding-energy relation for predicting equilibrium interfacial distances and adhesion energies; and the ideal work of separation as a measure of junction stability. In addition, we show that the established interpretation of the computed ideal work of separation might be misleading in predicting the optimal interface structures. Finally, we perform a detailed analysis of the atomic and interplanar relaxations in each junction, and identify their contributions to the tunnel barrier parameters. Our results imply that the structural irregularities on the surface of the Al film have a significant contribution to lowering the tunnel barrier height, while atomic relaxations at the interface and interplanar relaxations in Al 2 O 3 may considerably change the width of the barrier and, thus, distort its uniformity. Both the effects may critically influence the performance of the MIM tunnel devices.

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“…7 Subgap conductance of defect-free NIS junctions is dominated by two-particle Andreev tunneling. 8 For n qp , studies on superconducting qubits 2,3 and resonators 5 have reported a low-temperature saturation to 10-55 μm −3 due to an unidentified excitation mechanism. Recently, a significantly improved result n qp < 1 μm −3 has been obtained by a transmon qubit realization.…”

Section: Introductionmentioning

confidence: 99%