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Andreone, A.; Cassinese, A.; Chiara, A. Di; Vaglio, R.; Gupta, Arunava; Sarnelli, E.

doi:10.1103/physrevb.49.6392

Cited by 82 publications

(44 citation statements)

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“…The normal resistance times junction area, ρ n , of the 24 • tilt GBJs ranged between 1.5 and 8 × 10 −6 Ωcm 2 and was more than an order of magnitude larger for the 36.8 • tilt GBJs. [11,12,19,20]. The observation of a clear gap structure and the temperature independent conductance well above V g strongly suggest that the dominating transport mechanism in the NCCO-GBJs is elastic tunneling.…”

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Superconducting Nd1.85Ce0.15CuO4−y bicrystal grain boundary Josephson junctions

Kleefisch

Alff

Schoop

et al. 1998

Applied Physics Letters

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We have studied the electric transport properties of symmetrical [001] tilt Nd1.85Ce0.15CuO4−y (NCCO) bicrystal grain boundary Josephson junctions (GBJs) fabricated on SrTiO3 bicrystal substrates with misorientation angles of 24 • and 36.8 • . The superconducting properties of the NCCOGBJs are similar to those of GBJs fabricated from the hole doped high temperature superconductors (HTS). The critical current density Jc decreases strongly with increasing misorientation angle. The products of the critical current Ic and the normal resistance Rn (∼ 100 µV at 4.2 K) are small compared to the gap voltage and fit well to the universal scaling law IcRn ∝ √ Jc found for GBJs fabricated from the hole doped HTS. This suggests that the symmetry of the order parameter, which most likely is different for the electron and the hole doped HTS has little influence on the characteristic properties of symmetrical [001] tilt GBJs. PACS: 74.25.Fy, 74.50.+r Applied Physics Letters to be published June 1, 1998Bicrystal grain boundary Josephson junctions (GBJs) have been studied intensively using epitaxial thin films of the various hole doped high temperature superconductors (HTS) [1][2][3]. However, there is very limited information on GBJs fabricated from the electron doped material Nd 1.85 Ce 0.15 CuO 4−y (NCCO) [4]. For the vast majority of GBJs the transport properties can be well described within the intrinsically shunted junction (ISJ) model [2,5,6]. In this model a continuous, but spatially inhomogeneous insulating grain boundary barrier is assumed that contains a high density of localized defect states. The localized states allow for resonant tunneling of quasiparticles providing an intrinsic resistive shunt, whereas resonant tunneling of Cooper pairs is prevented by Coulomb repulsion. This results in reduced I c R n products and a scaling behavior I c R n ∝ √ J c observed in many experiments [2,[5][6][7]. Meanwhile, it is well established that most hole doped HTS have a dominant d-wave component of the order parameter (OP) [8]. The influence of the d-wave symmetry of the OP on the magnetic field dependence of I c has been shown for asymmetric 45 • tilt YBCO-GBJs [9]. So far, in the ISJ-model the likely d-wave pairing state of the hole doped HTS has not been taken into account and the relevance of the d-wave symmetry of the OP for the characteristic properties of symmetrical [001] tilt GBJs such as the small value and the scaling behavior of the I c R n product is still a point of controversy. To clarify this issue we have studied [001] tilt NCCO-GBJs. Since for the electron doped material NCCO there is convincing experimental evidence for a s-wave symmetry of the OP [10-13], NCCO-GBJs represent an interesting model system to test the influence of the OP symmetry on the transport properties of GBJs.The NCCO-GBJs were fabricated by molecular beam epitaxy (MBE) of c-axis oriented NCCO thin films on SrTiO 3 bicrystal substrates. The substrate temperature during growth was about 730 • C and ozone was used as oxidation gas. For ...

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“…To clarify this issue we have studied [001] tilt NCCO-GBJs. Since for the electron doped material NCCO there is convincing experimental evidence for a s-wave symmetry of the OP [10][11][12][13], NCCO-GBJs represent an interesting model system to test the influence of the OP symmetry on the transport properties of GBJs.…”

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confidence: 99%

Superconducting Nd1.85Ce0.15CuO4−y bicrystal grain boundary Josephson junctions

Kleefisch

Alff

Schoop

et al. 1998

Applied Physics Letters

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“…The analysis of this material is of particular interest with respect to the question whether or not there is a change in sign of the order parameter for NCCO. Up to now, there is convincing experimental evidence that NCCO has a dominating s-wave symmetry of the order parameter [18,19,20,21], i.e., the order parameter of NCCO is expected to show no change in sign for different k-directions. Hence, Andreev bound states are expected only for hole doped HTS, which are believed to have a dominating dwave symmetry of the order parameter, but should be absent for NCCO.…”

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confidence: 99%

Andreev bound states in high temperature superconductors

et al. 1998

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Abstract. Andreev bound states at the surface of superconductors are expected for any pair potential showing a sign change in different k-directions with their spectral weight depending on the relative orientation of the surface and the pair potential. We report on the observation of Andreev bound states in high temperature superconductors (HTS) employing tunneling spectroscopy on bicrystal grain boundary Josephson junctions (GBJs). The tunneling spectra were studied as a function of temperature and applied magnetic field. The tunneling spectra of GBJ formed by YBa2Cu3O 7−δ (YBCO), Bi2Sr2CaCu2O 8+δ (BSCCO), and La1.85Sr0.15CuO4 (LSCO) show a pronounced zero bias conductance peak that can be interpreted in terms of Andreev bound states at zero energy that are expected at the surface of HTS having a d-wave symmetry of the order parameter. In contrast, for the most likely s-wave HTS Nd1.85Ce0.15CuO4−y (NCCO) no zero bias conductance peak was observed. Applying a magnetic field results in a shift of spectral weight from zero to finite energy. This shift is found to depend nonlinearly on the applied magnetic field. Further consequences of the Andreev bound states are discussed and experimental evidence for anomalous Meissner currents is presented.

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“…All these requirements are met by superconducting stripline resonators where the sample acts as one of the ground planes. Superconducting stripline (also called triplate) resonators, [35][36][37][38][39] as well as the similar microstrip resonators, [40][41][42][43] have been used since the 1980s to study thin films of superconductors. A related technique are superconducting coplanar resonators, which have also been used to study the microwave properties of superconducting thin films, 44,45 and which recently became very popular for photon detection (as microwave kinetic inductance detectors) 46,47 and in the field of quantum information science (e.g.…”

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confidence: 99%

Surface-resistance measurements using superconducting stripline resonators

Hafner

Dressel

Scheffler

2014

Review of Scientific Instruments

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We present a method to measure the absolute surface resistance of conductive samples at a set of GHz frequencies with superconducting lead stripline resonators at temperatures 1 -6 K. The stripline structure can easily be applied for bulk samples and allows direct calculation of the surface resistance without the requirement of additional calibration measurements or sample reference points. We further describe a correction method to reduce experimental background on high-Q resonance modes by exploiting TEM-properties of the external cabling. We then show applications of this method to the reference materials gold, tantalum, and tin, which include the anomalous skin effect and conventional superconductivity. Furthermore, we extract the complex optical conductivity for an all-lead stripline resonator to find a coherence peak and the superconducting gap of lead.

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Temperature dependence of the penetration depth inNd1.85Ce0.15<

Cited by 82 publications

References 13 publications

Superconducting Nd1.85Ce0.15CuO4−y bicrystal grain boundary Josephson junctions

Superconducting Nd1.85Ce0.15CuO4−y bicrystal grain boundary Josephson junctions

Andreev bound states in high temperature superconductors

Surface-resistance measurements using superconducting stripline resonators

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