Superconductivity and the Josephson effect in a periodic array of NbInAsNb junctions

Drexler, H.; Harris, J.; Yuh, E.L.; Wong, K. C.; Allen, S. J.; Gwinn, E. G.; Kroemer, H.; Hu, Evelyn L.

doi:10.1016/0039-6028(96)00409-8

Cited by 11 publications

(14 citation statements)

References 12 publications

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“…A similar arrangement has been studied previously [14,15] in low magnetic fields. An important difference to single S-2DEG-S junctions is that the voltage Right: A scanning electron micrograph of the sample taken at the mesa edge.…”

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confidence: 78%

Andreev Reflection at High Magnetic Fields: Evidence for Electron and Hole Transport in Edge States

et al. 2005

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We have studied magnetotransport in arrays of niobium filled grooves in an InAs/AlGaSb heterostructure. The critical field of up to 2.6 T permits to enter the quantum Hall regime. In the superconducting state, we observe strong magnetoresistance oscillations, whose amplitude exceeds the Shubnikov-de Haas oscillations by a factor of about two, when normalized to the background. Additionally, we find that above a geometry-dependent magnetic field value the sample in the superconducting state has a higher longitudinal resistance than in the normal state. Both observations can be explained with edge channels populated with electrons and Andreev reflected holes.The analysis of superconductor-semiconductor structures has been an active field of research in recent years (see, e.g., Ref. 1 and references therein). The versatility of semiconductors and the high mobilities attainable in heterostructures in combination with the retroreflecting and phase coherent process of Andreev reflection [2] have allowed to observe a number of unique phenomena. By now, experiments in the regime of low magnetic fields, i.e. no larger than a few flux quanta per junction area, are well established. Gateable Josephson currents [3], quasiparticle interference [4], phase coherent oscillations [5] and an induced superconducting gap [6] have been observed, to name a few.In the high-field regime, experimental evidence is much less abundant. A number of theoretical papers have dealt with Andreev reflection at high fields [7,8,9,10]. Notably, Ref. 7 describes how edge channels in the quantum Hall regime are formed of electron and hole states. To enter the regime of a fully developed quantum Hall effect external fields of several Tesla are required. Experiments have been performed with high critical field superconductors, such as NbN [11,12] or sintered SnAu [13], each of which suffer from technological difficulties, making the interpretation of the experiments in the quantum Hall regime difficult. In this work, however, we report clear evidence of the influence of Andreev reflection on transport in edge states using the well established Nb-InAs system. The critical field of up to 2.6 T permits to enter the quantum Hall regime at high filling factors.For the sample geometry we have chosen an array of niobium filled grooves in an InAs-AlGaSb heterostructure containing a high-mobility two-dimensional electron gas (2DEG). A similar arrangement has been studied previously [14,15] in low magnetic fields. An important difference to single S-2DEG-S junctions is that the voltage Right: A scanning electron micrograph of the sample taken at the mesa edge. A cross section of the sample is also shown.

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confidence: 78%

Andreev Reflection at High Magnetic Fields: Evidence for Electron and Hole Transport in Edge States

et al. 2005

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“…The latter include Refs. [5][6][7][8] which displayed intriguing frequency-doubling effects and thus motivated the development of the theory presented here (an interpretation in terms of the frequency-doubling effects predicted in the early eighties by Spivak and coworkers [9] was initially proposed, but had to be rejected [10]). Theoretically, NEQ phenomena have been studied in both clean [11][12][13] and dirty [14][15][16][17][18] limits.…”

Section: Introductionmentioning

confidence: 99%

Nonequilibrium Josephson-like effects in wide mesoscopic SNS junctions

Argaman

1999

Superlattices and Microstructures

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Mesoscopic superconducting-normal-metal-superconducting (S-N-S) junctions with a large separation between the superconducting electrodes (i.e. wide junctions) exhibit nonequilibrium supercurrents, even at temperatures for which the equilibrium Josephson effect is exponentially small. The second harmonic of the Josephson frequency dominates these currents, as observed in recent experiments. A simple description of these effects, in the spirit of the Resistively-Shunted-Junction model, is suggested here. It is used to calculate dc I-V characteristics, and to examine the effects of various types of noise and of external microwave radiation (Shapiro steps). It is found that the nonequilibrium supercurrents are excited when the junction is driven by a dc bias or an ac bias, or even by external noise. In the case of junctions which are also long in the direction perpendicular to the current flow, thermodynamic phase fluctuations (thermal noise) alone can drive the quasiparticles out of local equilibrium. Magnetic flux is then predicted to be trapped in units of Φ0/2 = hc/4e.

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“…It is clear that the halfinteger and small 1/4 step are much weaker functions of temperature than the other steps, most notably than the integer Shapiro step. This behavior is more remarkable considering that at temperatures above 5 K the CVC of the device is completely resistive, indicating that I c ≈ 0; nevertheless, the half-integer step can be resolved within a few 100 mK of the transition temperature of the Nb electrodes [9]. These results were our first evidence of ac supercurrents flowing at twice the Josephson frequency and at a temperature above the disappearance of the dc Josephson effect.…”

Section: Resultsmentioning

confidence: 78%