Using ion irradiation to make high-Tc Josephson junctions

Bergeal, N.; Lesueur, J.; Sirena, M.; Faini, G.; Aprili, M.; Contour, J. P.; Léridon, Brigitte

doi:10.1063/1.2796105

Cited by 55 publications

(46 citation statements)

References 32 publications

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“…c-axis trilayer structures YBCO(Co)/PBCGO/NdBCO have been grown on SrTi0 3 (100) substrates by pulsed laser deposition and covered by an in situ gold layer. Lithography and a high-energy (250 keV) ion irradiation technique through an in situ gold mask have been used to design trilayer junctions 28 .…”

Section: Methodsmentioning

confidence: 99%

Pairing fluctuations in the pseudogap state of copper-oxide superconductors probed by the Josephson effect

et al. 2008

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The phase diagram of high-temperature superconductors is still to be understood 1 . In the low-carrier-doping regime, a loss of spectral weight in the electronic excitation spectrum-the so-called pseudogap-is observed above the superconducting temperature T c , and below a characteristic temperature T * (ref. 2). First observed in the spin channel by NMR measurements, the pseudogap has also been observed in the charge channel by scanning probe microscopy and photoemission experiments, for instance 2 . An important issue to address is whether this phenomenon is related to superconductivity or to a competing 'hidden' order. In the superconductivity case, it has been suggested that superconducting pairing fluctuations may be responsible, but this view remains to be tested experimentally. Here, we have designed a Josephson-like experiment to probe directly the fluctuating pairs in the normal state. We show that fluctuations survive only in a restricted range of temperature above T c , well below T * , and therefore cannot explain the opening of the pseudogap at higher temperature.Angle-resolved photoemission spectroscopy 3,4 and scanning tunnelling spectroscopy 5 showed a characteristic energy of the pseudogap that merges with the superconducting gap when the temperature is lowered below T c . This reveals a smooth crossover rather than a sharp transition line between the pseudogap regime and the superconducting state, and has led to the superconducting precursor scenario. As opposed to the conventional Bardeen-Cooper-Schrieffer (BCS) transition, where pairing and condensation occur simultaneously at T c , in underdoped cuprates fluctuating pairs may form at T * , with no long-range coherence, and condense in the superconducting state at T c (refs 6,7). Difficulties in confirming (or invalidating) this scenario arise from the fact that most of the experimental techniques used to investigate the pseudogap are sensitive only to the one-particle excitations, and therefore cannot provide a test of pairing above T c . Owing to its ability to probe the properties of the superconducting wavefunction, the Josephson effect is a natural way to address the fluctuation issue.In a second-order phase transition, the susceptibility is given by the linear response of the order parameter to a suitable external field. In the case of the superconducting phase transition, the role of the external field can be played by the rigid pair field of a second superconductor below its own T c (refs 8,9). In a Josephson junction in which one side of the junction is the fluctuating superconductor of interest above its T c , whereas the other side is a superconductor below its T c , the coupling between the pairing fluctuations and the well-established pair field gives rise to an excess current I ex proportional to the imaginary part of the frequency-and wavenumber-dependent pair susceptibility χ(ω, q). For a conventional superconductor above its T c (ref. 9)where Γ 0 = (16k B /h)(T − T c ) is the relaxation rate of the fluctuations, ξ(T ) is the ...

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Section: Methodsmentioning

confidence: 99%

Pairing fluctuations in the pseudogap state of copper-oxide superconductors probed by the Josephson effect

et al. 2008

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“…An alternative technology to make large arrays of HTSc SQUIDs is the irradiation technique developed by the San Diego group [17,18], and more recently by Bergeal et al [19,20]. Starting from a commercial YBCO film, the circuit and the JJ are patterned by ion-irradiation through photoresist masks.…”

Section: High-tc Superconducting Quantum Interference Filters (Sqifs)mentioning

confidence: 99%

High-Tc superconducting quantum interference filters (SQIFs) made by ion irradiation

Ouanani

Kermorvant

Ulysse

et al. 2016

Supercond. Sci. Technol.

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Abstract.Superconducting Quantum Interference Filters (SQIFs) are arrays of superconducting loops of different sizes including Josephson Junctions (JJ). For a random distribution of sizes, they present a non-periodic response to an applied magnetic field, with a large transfer function and a magnetic field sensitivity potentially improved with respect to that of a single SQUID. Such properties make SQIFs interesting devices arXiv:1603.07592v2 [cond-mat.supr-con] 1 Jun 2016High-Tc Superconducting Quantum Interference Filters (SQIFs) made by ion irradiation2 to detect the magnetic component of electromagnetic waves at microwave frequencies.We have used the highly scalable technique of ion irradiation to make SQUIDs and SQIFs based on commercial YBa 2 Cu 3 O 7 films, and studied their properties. Both display optimum performances as a function of temperature and bias current, that can be understood in the frame of numerical simulations that we developed. The role of asymmetries and dispersion in JJ characteristics (routinely found in High Tc Superconductors technologies) is also studied. We have found that both do not impede the existence of a SQIF effect but play a role on the emergence of the optimal point. We finally present results on SQIF made with 2000 SQUID in series, showing a transfer function dV /dB ∼ 1000V /T .

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“…figure 1). The estimated depth range is 220 nm and in these conditions the parameter quantifying the effect of ion irradiation in the system is expected to be the mean value of the depth damage distribution [20]. Considering this, the final dpa factor can be easily evaluated by dpa = 10 .…”

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“…We also present a simple method to quantify the structural damage in terms of a more "universal" magnitude than the irradiation dose: the number of defects per atom (dpa) of the structure. This magnitude better expresses the implantation damage done in the system and has proven to give excellent results as a parameter of the influence of point defect disorder in the physical properties of irradiated High Tc superconductor films [20].…”

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Influence of ion implantation on the magnetic and transport properties of manganite films

et al. 2010

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We have used oxygen ions irradiation to generate controlled structural disorder in thin manganite films. Conductive atomic force microscopy CAFM), transport and magnetic measurements were performed to analyze the influence of the implantation process in the physical properties of the films. CAFM images show regions with different conductivity values, probably due to the random distribution of point defect or inhomogeneous changes of the local Mn3+/4+ ratio to reduce lattice strains of the irradiated areas. The transport and magnetic properties of these systems are interpreted in this context. Metal-insulator transition can be described in the frame of a percolative model. Disorder increases the distance between conducting regions, lowering the observed T MI . Point defect disorder increases localization of the carriers due to increased disorder and locally enhanced strain field. Remarkably, even with the inhomogeneous nature of the samples, no sign of low field magnetoresistance was found.Point defect disorder decreases the system magnetization but doesn't seem to change the magnetic transition temperature. As a consequence, an important decoupling between the 2 magnetic and the metal-insulator transition is found for ion irradiated films as opposed to the classical double exchange model scenario.Pacs: 71.30.+h, 75.47.Lx

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Using ion irradiation to make high-Tc Josephson junctions

Cited by 55 publications

References 32 publications

Pairing fluctuations in the pseudogap state of copper-oxide superconductors probed by the Josephson effect

Pairing fluctuations in the pseudogap state of copper-oxide superconductors probed by the Josephson effect

High-Tc superconducting quantum interference filters (SQIFs) made by ion irradiation

Influence of ion implantation on the magnetic and transport properties of manganite films

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