Tunneling through Ultrasmall NIS Junctions in Terms of Andreev Reflection. A Nonlinear Response Approach

Hädicke, A.; Krech, W.

doi:10.1002/pssb.2221910114

Cited by 3 publications

(3 citation statements)

References 20 publications

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“…To determine which is responsible, and to confirm the cause of the flat region, we examine theoretically the rates for all processes. Using existing formulas from earlier work on normal metal insulator superconductor (NIS) junctions, we calculate rates for quasiparticle tunneling [30] and Andreev reflection [31,32] from each of the leads. The former follow from Fermi's golden rule, while the latter are derived using a nonlinear response approach.…”

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confidence: 99%

Experimental observation of the breaking and recombination of single Cooper pairs

et al. 2014

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We observe the real-time breaking of single Cooper pairs by monitoring the radio-frequency impedance of a superconducting double quantum dot. The Cooper pair breaking rate in the microscale islands of our device decreases as temperature is reduced, saturating at 2 kHz for temperatures beneath 100 mK. In addition, we measure in real time the quasiparticle recombination into Cooper pairs. Analysis of the recombination rates shows that, in contrast to bulk films, a multistage recombination pathway is followed. Unpaired electronic excitations-quasiparticles-play an important role in determining the behavior of superconducting electrical devices. They lead to even-odd parity effects in Coulomb blockade nanostructures [1,2]; they act as a source of decoherence in superconducting qubits [3]; they cause generation-recombination noise in superconducting resonators [4]; they may be important in superconductingnormal devices for Majorana fermionics [5]; and, importantly, they enable the detection of far-infrared light, for example, in kinetic inductance detectors [6]. In this Rapid Communication we investigate the generation and recombination of single quasiparticle pairs in a superconducting double dot (SDD), a Coulomb blockade nanostructure. Double quantum dots have been widely investigated in the context of semiconducting spin qubits where they enable electrostatic control and measurement over electron spins and spin pairs [7]. Previously, semiconductor double dots have been integrated with superconducting leads, allowing electrostatically tunable supercurrents [8] and the splitting of Cooper pair currents into spatially separated and correlated electron currents [9][10][11]. However, apart from an early study investigating the superconducting double quantum dot as a qubit architecture [12], there have been few studies of this system, thus motivating our current work.We investigate the quasiparticle dynamics in the SDD, therefore, our results are relevant to the long-standing quasiparticle poisoning problem in superconducting qubits [13,14]. It has long been known that incoherent quasiparticle tunneling interrupts the coherent tunneling of Cooper pairs. Quasiparticle poisoning is hence a serious issue in charge-based * ajf1006@cam.ac.uk superconducting qubits [15] and has recently been shown to be relevant in the case of low-charging energy transmon qubits [16]. Experiments on superconducting qubits have shown that by taking extreme care over filtering infrared radiation it is possible to extend coherence times, presumably because of the lower quasiparticle temperatures achieved [17]. Quasiparticle tunneling into a Cooper pair box has been used to detect far-infrared radiation from a blackbody source with a noise-equivalent power of less than 10 −19 W/Hz 1/2 , potentially providing a successor technology to kinetic inductance detectors [18]. In parallel, studies on superconducting resonators have shown a saturation of the quasiparticle population at a relatively high temperature of 140 mK [19]. It remains an experimenta...

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confidence: 99%

Experimental observation of the breaking and recombination of single Cooper pairs

et al. 2014

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“…The important feature of this novel Andreev process is that it appears in lowest (first) order approximation with respect to the tunneling barrier transparencythe same order as the usual tunneling current exhibiting the pseudogap. This effect is stronger than the standard Andreev conductance of a N-I-S junction which is proportional to the square of the transparency 11,12 . The reason is that the fluctuation-induced domain of superconducting phase in the biased electrode is not separated from the surrounding normal phase by any barrier and thus the process of Andreev-like reflection does not involve an additional tunneling process.…”

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confidence: 82%

Low-Bias-Anomaly and Tunnel Fluctuoscopy

Glatz¹,

Varlamov²,

Винокур³

2013

Preprint

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Electron tunneling spectroscopy pioneered by Esaki 1 and Giaever 2,3 offered a powerful tool for studying electronic spectra and density of states (DOS) in superconductors. This led to important discoveries that revealed, in particular, the pseudogap in the tunneling spectrum of superconductors above their critical temperatures 4-7 . However, the phenomenological approach of Ref. 3 does not resolve the fine structure of low-bias behavior carrying significant information about electron scattering, interactions, and decoherence effects. Here we construct a complete microscopic theory of electron tunneling into a superconductor in the fluctuation regime. We reveal a non-trivial lowenergy anomaly in tunneling conductivity due to Andreev-like reflection of injected electrons from superconducting fluctuations. Our findings enable real-time observation of fluctuating Cooper pairs dynamics by time-resolved scanning tunneling microscopy measurements and open new horizons for quantitative analysis of the fluctuation electronic spectra of superconductors.

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“…(11), which makes the effect strongly temperature dependent close to the transition point. The discovered LBA, appearing already in the first order of the transparency, qualitatively differs from the well-known Andreev conductance of a superconducting micro-constriction [19], occurring below the transition temperature, which rapidly disappears when the latter departs from the metallic towards the tunneling regime (in the classical paper [19] this decrease is governed by an additional factor Z 2 (Z is a dimensionless interfacial scattering strength) to transparency, which vanishes for an insulating barrier, while the authors of [20] explicitly demonstrated that the Andreev conductance of a N-I-S junction is directly proportional to the square of its transparency). The reason for this discrepancy is that the fluctuation-induced superconducting regions in the biased electrode are not separated by any barrier from the surrounding normal phase and thus the process of Andreev reflection does not involve an additional tunneling process.…”

Section: (C))mentioning

confidence: 92%

High-resolution tunnel fluctuoscopy

Glatz

Varlamov

Vinokur

2014

EPL

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Electron tunneling spectroscopy pioneered by Esaki and Giaever offered a powerful tool for studying electronic spectra and density of states (DOS) in superconductors. This led to important discoveries that revealed, in particular, the pseudogap in the tunneling spectrum of superconductors above their critical temperatures. However, the phenomenological approach of Giaever and Megerle does not resolve the fine structure of low-bias behavior carrying significant information about electron scattering, interactions, and decoherence effects. Here we construct a complete microscopic theory of electron tunneling into a superconductor in the fluctuation regime. We reveal a non-trivial low-energy anomaly in tunneling conductivity due to Andreev-like reflections of injected electrons from superconducting fluctuations. Our findings enable real-time observation of fluctuating Cooper pairs dynamics by time-resolved scanning tunneling microscopy measurements and open new horizons for quantitative analysis of the fluctuation electronic spectra of superconductors.

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Tunneling through Ultrasmall NIS Junctions in Terms of Andreev Reflection. A Nonlinear Response Approach

Cited by 3 publications

References 20 publications

Experimental observation of the breaking and recombination of single Cooper pairs

Experimental observation of the breaking and recombination of single Cooper pairs

Low-Bias-Anomaly and Tunnel Fluctuoscopy

High-resolution tunnel fluctuoscopy

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