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

Kleefisch, S.; Alff, Lambert; Schoop, U.; Marx, Achim; Gross, Rudolf; Naito, Makio; Sato, Hisashi

doi:10.1063/1.121449

Cited by 27 publications

(22 citation statements)

References 24 publications

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“…This indicates the presence of negative currents due to the d-wave symmetry of the OP in the electrodes [20]. In contrast, the I c (H) patterns of NCCOand PCCO-GBJs are close to a regular Fraunhofer diffraction pattern expected for an ideal Josephson junction [13]. Finally, the tunneling spectra measured for NCCO do not show any zero bias anomaly giving strong evidence for the absence of a sign change in the superconducting pair potential [5,18,21].…”

mentioning

confidence: 75%

“…A detailed description of the fabrication process was given by Naito et al [12]. Josephson behavior in NCCO-GBJs has been demonstrated by Kleefisch et al [13]. We stress that the demonstration of the Josephson effect for both NCCO and PCCO, the low resistivity values (below 50 µΩcm at 25 K) and the T c value of about 24 K demonstrate that the thin film samples are optimum doped, well oxygen reduced, and single phase.…”

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confidence: 94%

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Anomalous Low Temperature Behavior of SuperconductingNd1.85Ce0.15CuO4−

Alff¹,

Meyer²,

Kleefisch³

et al. 1999

Phys. Rev. Lett.

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119

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We have measured the temperature dependence of the in-plane London penetration depth λ ab (T ) and the maximum Josephson current Ic(T ) using bicrystal grain boundary Josephson junctions of the electron-doped cuprate superconductor Nd1.85Ce0.15CuO4−y. Both quantities reveal an anomalous temperature dependence below about 4 K. In contrast to the usual monotonous decrease (increase) of λ ab (T ) (Ic(T )) with decreasing temperature, λ ab (T ) and Ic(T ) are found to increase and decrease, respectively, with decreasing temperature below 4 K resulting in a non-monotonous overall temperature dependence. This anomalous behavior was found to be absent in analogous measurements performed on Pr1.85Ce0.15CuO4−y. From this we conclude that the anomalous behavior of Nd1.85Ce0.15CuO4−y is caused by the presence of the Nd 3+ paramagnetic moments. Correcting the measured λ ab (T ) dependence of Nd1.85Ce0.15CuO4−y for the temperature dependent susceptibility due to the Nd moments, an exponential dependence is obtained indicating isotropic s-wave pairing. This result is fully consistent with the λ ab (T ) dependence measured for Pr1.85Ce0.15CuO4−y. The vast majority of experiments on the cuprate superconductors are performed on hole-doped materials. Much less attention has been paid to the system Ln 2−x Ce x CuO 4−y (with Ln = Pr, Nd, Sm, Eu) [1] which represents an electron-doped material. Both hole-and electron-doped cuprates have in common the copper oxygen planes as the central building blocks of the high-temperature superconductors (HTS) suggesting similar superconducting properties. However, as can already be seen from the differences of the generic phase diagram on the electron-and hole-doped side, the physics of electron-and hole-doped HTS is different. In particular, the order parameter (OP) symmetry of the electron-doped cuprates is most likely of s-wave type [2][3][4][5], in contrast to the d-wave OP symmetry in the hole-doped HTS. To clarify the specific differences and similarities between the electron-and hole-doped HTS a more detailed experimental study of the electron-doped HTS is required.

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confidence: 75%

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confidence: 94%

Anomalous Low Temperature Behavior of SuperconductingNd1.85Ce0.15CuO4−

Alff¹,

Meyer²,

Kleefisch³

et al. 1999

Phys. Rev. Lett.

Self Cite

119

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“…These values are about two order of magnitude smaller than the intrinsic bulk values. Similarly, the observed I c R N value in the NCCO and PCCO tricrystal experiments is about 0.1 mV, as inferred from the measured critical current density J c = 6 A/cm 2 [20] and the empirical relation between I c R N and J c [62]. This I c R N value is also about two order of magnitude smaller than the intrinsic bulk value, which is estimated to be ∼ 8 mV with ∆ M (0) = 2.5T c [56].…”

Section: Phase-sensitive Experiments Along the Ab-planesmentioning

confidence: 86%

Identification of the bulk pairing symmetry in high-temperature superconductors: Evidence for an extendedswave with eight line nodes

Zhao

2001

Phys. Rev. B

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we identify the intrinsic bulk pairing symmetry for both electron and hole-doped cuprates from the existing bulk-and nearly bulk-sensitive experimental results such as magnetic penetration depth, Raman scattering, single-particle tunneling, Andreev reflection, nonlinear Meissner effect, neutron scattering, thermal conductivity, specific heat, and angle-resolved photoemission spectroscopy. These experiments consistently show that the dominant bulk pairing symmetry in hole-doped cuprates is of extended s-wave with eight line nodes, and of anisotropic s-wave in electron-doped cuprates. The proposed pairing symmetries do not contradict some surface-and phase-sensitive experiments which show a predominant d-wave pairing symmetry at the degraded surfaces. We also quantitatively explain the phase-sensitive experiments along the c-axis for both Bi2Sr2CaCu2O8+y and YBa2Cu3O7−y.

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“…A key feature of the ISJ-model is the fact that the transport of Cooper pairs via the localized states is prevented by Coulomb repulsion, i.e. Cooper pairs have to use the direct tunneling channel, whereas due to the large density of defect states the quasiparticle transport is dominated by resonant tunneling via a single localized state [73,82,83,84,85,86,87]. The resonant channel can be viewed as to provide an intrinsic resistive shunt leading to the name intrinsically shunted junction.…”

Section: Transport Mechanism In Gbjsmentioning

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

Cited by 27 publications

References 24 publications

Anomalous Low Temperature Behavior of SuperconductingNd1.85Ce0.15CuO4−

Anomalous Low Temperature Behavior of SuperconductingNd1.85Ce0.15CuO4−

Identification of the bulk pairing symmetry in high-temperature superconductors: Evidence for an extendedswave with eight line nodes

Andreev bound states in high temperature superconductors

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