Experimental investigation of hybrid single-electron turnstiles with high charging energy

Kemppinen, A.; Kafanov, Sergey; Pashkin, Yu. A.; Tsai, Jaw-Shen; Averin, D. V.; Pekola, Jukka P.

doi:10.1063/1.3127229

Cited by 36 publications

(50 citation statements)

References 19 publications

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“…3(a)) demonstrates a negative deviation from its ideal value I = ef (red dashed line) at high A g values in the full agreement with the effect of backtunneling processes at high resistance/Coulomb energy [23]. The current I in low resistive samples L and R (black dots in panels (b) and (c)) with R T ∼ 2R Q exceeds ef by 0.7 % and 5 %, respectively.…”

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confidence: 67%

Interplay of the Inverse Proximity Effect and Magnetic Field in Out-of-Equilibrium Single-Electron Devices

et al. 2017

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The magnetic field is shown to affect significantly non-equilibrium quasiparticle (QP) distributions under conditions of inverse proximity effect on the remarkable example of a single-electron hybrid turnstile. This effect suppresses the gap in the superconducting leads in the vicinity of turnstile junctions with a Coulomb blockaded island, thus, trapping hot QPs in this region. Applied magnetic field creates additional QP traps in the form of vortices or regions with reduced superconducting gap in the leads resulting in release of QPs away from junctions. We present clear experimental evidence of such interplay of the inverse proximity effect and a magnetic field revealing itself in the superconducting gap enhancement in a magnetic field as well as in significant improvement of the turnstile characteristics. The observed interplay of the inverse proximity effect and external magnetic field, and its theoretical explanation in the context of QP overheating are important for various superconducting and hybrid nanoelectronic devices, which find applications in quantum computation, photon detection and quantum metrology.PACS numbers: 85.35. Gv, 74.25.Ha,74.45.+c, 73.23.Hk Proximity effect which induces superconducting correlations into a normal-metal conductor at the interface between a superconductor and a normal-metal conductor has been widely explored and plays an important role in the physics of superconductors [1]. Considering recent developments one can see that this phenomenon provides a basis for the engineering and manipulation of the symmetry of the induced superconducting pairing in various hybrid structures including topologically nontrivial systems known to host Majorana fermions [2] and possess other exciting properties [3][4][5]. The proximity phenomenon has an important counterpart, namely the inverse proximity effect, which is responsible for the reduction of the superconducting order parameter due to the penetration of electrons through the superconductor -normal metal interface [6]. Microscopically both the proximity and inverse proximity effects can be understood in terms of the Andreev reflection at the interface of a superconductor and a normal metal [7].Reducing the superconducting gap the inverse proximity effect provides a physical mechanism responsible for the formation of the traps for the nonequilibrium quasiparticles (QPs) known to affect the performance of many superconducting devices such as X-ray detectors [8,9], single photon detectors [10], refrigerators based on normal metal (N) -insulator (I) -superconductor (S) junctions [11], superconducting resonators [12], superconducting qubits [13], and single-electronic hybrid turnstiles [3]. The problem of heat evacuation in these devices is usually solved by introducing QP traps based on normal metal inclusions [15][16][17], on the local order parameter suppression by an external magnetic field [3,[11][12][13] or by using an alternative device design immune to QP overheating [18]. The traps arising from the inverse proximity phenomen...

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confidence: 67%

Interplay of the Inverse Proximity Effect and Magnetic Field in Out-of-Equilibrium Single-Electron Devices

et al. 2017

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“…[25] are quite different from ours, their situation resembles ours in the sense that photons with a very high frequency of Á=h * 50 GHz are responsible for tunneling. SINIS turnstile.-As a practical application, we discuss the SINIS turnstile, which is a hybrid single-electron transistor (SET) and a strong candidate for realizing the unit ampere in quantum metrology [4,[27][28][29][30]. In the previous experimental studies [4,27,29], its accuracy was limited by the subgap leakage.…”

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confidence: 99%

“…SINIS turnstile.-As a practical application, we discuss the SINIS turnstile, which is a hybrid single-electron transistor (SET) and a strong candidate for realizing the unit ampere in quantum metrology [4,[27][28][29][30]. In the previous experimental studies [4,27,29], its accuracy was limited by the subgap leakage. Here we test the influence of the ground plane on the flatness of the current plateaus at multiples of ef, where f is the operating frequency.…”

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Environment-Assisted Tunneling as an Origin of the Dynes Density of States

et al. 2010

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We show that the effect of a high-temperature environment in current transport through a normal metalinsulator-superconductor tunnel junction can be described by an effective density of states in the superconductor. In the limit of a resistive low-Ohmic environment, this density of states reduces into the well-known Dynes form. Our theoretical result is supported by experiments in engineered environments. We apply our findings to improve the performance of a single-electron turnstile, a potential candidate for a metrological current source. DOI: 10.1103/PhysRevLett.105.026803 PACS numbers: 73.40.Gk, 06.20.Jr, 72.70.+m, 73.20.At Introduction.-The density of states (DOS) of the carriers governs the transport rates in a mesoscopic conductor [1], e.g., in a tunnel junction. Understanding the current transport in a junction in detail is of fundamental interest, but it plays a central role also in practical applications, for instance, in the performance of superconducting qubits [2], of electronic coolers and thermometers [3], and of a singleelectron turnstile to be discussed in this Letter [4]. When one or both of the contacts of a junction are superconducting, the one-electron rates at small energy bias should vanish at low temperatures because of the gap in the Bardeen-Cooper-Schrieffer (BCS) DOS [5]. Yet, a small linear in voltage leakage current persists in the experiments [3,6-10] that can often be attributed to the Dynes DOS, a BCS-like expression with lifetime broadening [11,12]. A junction between two leads admits carriers to pass at a rate that depends on the DOS of the conductors, the occupation of the energy levels, and the number of conduction channels in the junction [13]. In general, basic one-electron tunneling coexists with many-electron tunneling, for instance, cotunneling in multijunction systems [14], or Andreev reflection in superconductors [15,16]. However, when the junction is made sufficiently opaque, a common situation in practice, only one-electron tunneling governed by the Fermi golden rule should persist. We demonstrate experimentally that the subgap current in a high-quality opaque tunnel junction between a normal metal and a superconductor can be ascribed to photon-assisted tunneling. We show theoretically that this leads exactly to the Dynes DOS with an inverse lifetime of e 2 k B T env R=@ 2 , where T env and R are the temperature and effective resistance of the environment.We employ a tunnel junction with a normal metalinsulator-superconductor (NIS) structure; see Fig. 1(a). The essentially constant DOS in the normal metal renders

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“…The hybrid single-electron transistor (SET) has been intensively studied during the past few years to produce quantized current for metrological applications [14][15][16][17][18]. The rf refrigerator is based on the very same device concept: it is a SINIS-type structure composed of superconducting (S) source and drain leads tunnel coupled (I) to a very small normal-metal (N) island in the Coulomb blockade regime [see Fig.…”

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confidence: 99%

“…Typical experimental value for the smearing parameter for the aluminum thin films near the tunnel junction is $10 À4 [16,17].…”

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Single-Electronic Radio-Frequency Refrigerator

Kafanov¹,

Kemppinen

Pashkin

et al. 2009

Phys. Rev. Lett.

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Experimental investigation of hybrid single-electron turnstiles with high charging energy

Cited by 36 publications

References 19 publications

Interplay of the Inverse Proximity Effect and Magnetic Field in Out-of-Equilibrium Single-Electron Devices

Interplay of the Inverse Proximity Effect and Magnetic Field in Out-of-Equilibrium Single-Electron Devices

Environment-Assisted Tunneling as an Origin of the Dynes Density of States

Single-Electronic Radio-Frequency Refrigerator

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