Origin of Hysteresis in a Proximity Josephson Junction

Courtois, Hervé; Meschke, Matthias; Peltonen, Joonas T.; Pekola, Jukka P.

doi:10.1103/physrevlett.101.067002

Cited by 255 publications

(282 citation statements)

References 22 publications

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“…Here, we take into account the presence of the degenerately doped Si substrate, which provides the dominant contribution to the capacitance between the superconducting leads (tens of fF). An alternative explanation of hysteresis in a SNS junction could be overheating [12]. In our case, two samples (A and C) have very similar switching and retrapping currents.…”

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confidence: 88%

Phase Diffusion in Graphene-Based Josephson Junctions

et al. 2011

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We report on graphene-based Josephson junctions with contacts made from lead. The high transition temperature of this superconductor allows us to observe the supercurrent branch at temperatures up to ∼ 2 K, at which point we can detect a small, but non-zero, resistance. We attribute this resistance to the phase diffusion mechanism, which has not been yet identified in graphene. By measuring the resistance as a function of temperature and gate voltage, we can further characterize the nature of electromagnetic environment and dissipation in our samples. PACS numbers: 74.45.+c, 74.50.+r, 72.80.Vp Josephson junctions with a normal metal region sandwiched between two superconductors are known as superconductor-normal-superconductor (SNS) structures. Over the years, the normal region has been made from non-metallic nanostructures, including heterostructures, nanotubes, quantum wires, quantum dots [1], and, most recently, graphene [2][3][4][5]. Usually, these superconductor-graphene-superconductor (SGS) junctions employ aluminum as the superconducting metal, separated from graphene by another metal layer (often titanium) intended to create a good contact. In this paper, we succeed in making palladium-lead (Pd/Pb) contacts to graphene. Here, Pd is known to form low-resistance contacts to graphene [6,7], while Pb has the advantage of a relatively large critical temperature (7.2 K). As a result, the SGS junctions demonstrate an enhanced zerobias conductance up to temperatures of the order of 5 K, and at temperatures below ∼ 2 K a clearly visible supercurrent branch appears in the I − V curves.In all of our samples, a small, but non-zero voltage is observed below the switching current. We attribute this feature to the phase diffusion mechanism [8]. The phase diffusion in underdamped junctions is enabled by the junction's environment, which provides dissipation at high frequencies [9]. Observation of this regime in our SGS junctions is facilitated by the high critical temperature of Pb. We first study the phase diffusion resistance as a function of temperature, which allows us to extract the activation energy associated with the phase slips. Next, the phase diffusion is measured at different gate voltages, resulting in a consistent picture of the junction's environment and dissipation at high frequencies. This series of measurements allows us both to establish the phase diffusion regime in underdamped SGS junctions, and to analyze their behavior in terms of well-established models. Finally, we demonstrate an efficient way of controlling the junction by passing a current through one of the electrodes within the same structure: the locally created magnetic field modulates the critical current. Several periods of oscillations are visible, indicating the spatial uniformity of the junction.Graphene was prepared by a version of the conventional exfoliation recipe [10] from natural graphite stamped on RCA-cleaned Si/SiO 2 substrates. The samples were verified by Raman spectroscopy to be single atomic layer thick with low defect...

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confidence: 88%

Phase Diffusion in Graphene-Based Josephson Junctions

et al. 2011

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“…For long junctions, we observe an exponential scaling of the current through the [5, 6,10,11]. Note that in graphene v F is a constant, and δE is expected to be independent of the carrier density or the mobility , 17-21], which could be attributed to either underdamped junction dynamics [8,20], or to the self-heating by the retrapping current [1,23]. As discussed in the supplementary material, the second scenario is more likely for most of the range studied here.…”

Section: Oct 2016mentioning

confidence: 99%

“…Device dimensions are listed in the supplementary information [16]. [1,[17][18][19][20][21], which could be attributed to either underdamped junction dynamics [8,20], or to the self-heating by the retrapping current [1,23]. As discussed in the supplementary material, the second scenario is more likely for most of the range studied here.…”

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confidence: 99%

Ballistic Graphene Josephson Junctions from the Short to the Long Junction Regimes

et al. 2016

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We investigate the critical current, I C , of ballistic Josephson junctions made of encapsulated graphene/boron-nitride heterostructures. We observe a crossover from the short to the long junction regimes as the length of the device increases. In long ballistic junctions, I C is found to scale as ∝ exp(−k B T /δE). The extracted energies δE are independent of the carrier density and proportional to the level spacing of the ballistic cavity, as determined from Fabry-Perot oscillations of the junction normal resistance. As T → 0 the critical current of a long (or short) junction saturates at al level determined by the product of δE (or ∆) and the number of the junction's transversal modes.1 arXiv:1604.07320v3 [cond-mat.mes-hall] Oct 2016Encapsulated graphene/boron-nitride heterostructures emerged in the past year as a medium of choice for studying proximity-induced superconductivity in the ultra-clean limit [1][2][3][4]. These junctions support the ballistic propagation of superconducting currents across micron-scale graphene channels, and their critical current is gate-tunable across several orders of magnitude. In these devices, a rich phenomenology arises from the interplay of superconductivity with ballistic transport [1], cyclotron motion [2], and even the quantum Hall effect at high magnetic field [4]. In a superconductor -normal metal -superconductor (SNS) junction, single particles in the N region cannot enter the superconductor and therefore experience Andreev reflections at each S-N interface. This results in Andreev bound states (ABS), which are capable of 2 carrying superconducting current across the N region. In long ballistic junctions, the energy spectrum of the ABS is quantized with a level spacing of T is independent of V G . In the case of long ballistic graphene junctions, the inverse slope δE is expected to be independent of the carrier density and inversely proportional to L.In this work we study several ballistic junctions of different length and demonstrate that the temperature dependence of the critical current dramatically differs in the long and short regimes. For long junctions, we observe an exponential scaling of the current through the [5, 6,10,11]. Note that in graphene v F is a constant, and δE is expected to be independent of the carrier density or the mobility , 17-21], which could be attributed to either underdamped junction dynamics [8,20], or to the self-heating by the retrapping current [1,23]. As discussed in the supplementary material, the second scenario is more likely for most of the range studied here. Based on the measurements of the switching statistics [16,[24][25][26], in the following we will use the switching current to represent the true critical current of the junction, I C .In the hole-doped regime, the reflections of ballistic charge carriers from the n-doped contact interfaces yield the quantum ("Fabry-Perot") interference. A very similar oscillation pattern could be observed in the dependence of both the the normal conductance, G N , and the critica...

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“…Therefore, hysteresis in I-V curves [15,53] does not necessarily indicate canonical Josephson phase dynamics, even in the presence of a Fraunhofer magnetic field pattern [8]. It may rather arise as a result of local heating processes, possibly induced by intrinsic inhomogeneous composition unavoidable for high-J c junctions.…”

Section: What Happens In Josephson Junctions At High Critical Currentmentioning

confidence: 99%

What happens in Josephson junctions at high critical current densities

Massarotti¹,

Stornaiuolo²,

Lucignano³

et al. 2017

Low Temperature Physics

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The impressive advances in material science and nanotechnology are more and more promoting the use of exotic barriers and/or superconductors, thus paving the way to new families of Josephson junctions. Semiconducting, ferromagnetic, topological insulator and graphene barriers are leading to unconventional and anomalous aspects of the Josephson coupling, which might be useful to respond to some issues on key problems of solid state physics. However, the complexity of the layout and of the competing physical processes occurring in the junctions is posing novel questions on the interpretation of their phenomenology. We classify some significant behaviors of hybrid and unconventional junctions in terms of their first imprinting, i.e. current-voltage curves, and propose a phenomenological approach to describe some features of junctions characterized by relatively high critical current densities J c . Accurate arguments on the distribution of switching currents will provide quantitative criteria to understand physical processes occurring in high-J c junctions. These notions are universal and apply to all kinds of junctions.

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Origin of Hysteresis in a Proximity Josephson Junction

Cited by 255 publications

References 22 publications

Phase Diffusion in Graphene-Based Josephson Junctions

Phase Diffusion in Graphene-Based Josephson Junctions

Ballistic Graphene Josephson Junctions from the Short to the Long Junction Regimes

What happens in Josephson junctions at high critical current densities

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