Symmetry of the order parameter in the high-Tc superconductor YBa2Cu3O7- δ

Kirtley, J. R.; Tsuei, C. C.; Sun, Jian; C., C.; Yu-Jahnes, Lock See; Gupta, A.; Rupp, M.; Ketchen, M. B.

doi:10.1038/373225a0

Cited by 343 publications

(145 citation statements)

References 17 publications

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“…1,2 One question that arises is whether the pairing symmetry is affected by doping. The symmetry of the superconducting order parameter for the optimally doped HTS's is consistent with d x 2 Ϫy 2( d-wave͒ as found in angle-resolved photoemission spectroscopy 3,4 ͑ARPES͒ experiments on Bi 2 Sr 2 CaCu 2 O 8ϩ␦ ͑Bi-2212͒ and tricrystal ring 5,6 experiments on YBa 2 Cu 3 O 7Ϫx and Tl 2 Ba 2 CuO 6ϩ␦ . The possibility of gap symmetry conversion from d-wave to s-wave with overdoping of Bi-2212 is suggested by Kendziora et al 7 and Kelley et al 8 using Raman and ARPES studies respectively.…”

Section: Introductionsupporting

confidence: 52%

Quasiparticle and Josephson tunneling of overdopedBi2Sr2CaCu2<

2000

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The point contact tunneling technique is used to examine quasiparticle and Josephson currents in overdoped Bi 2 Sr 2 CaCu 2 O 8ϩ␦ ͑Bi-2212͒ single crystals with bulk T c values ranging from 82 K down to 62 K. Superconductor-insulator-normal-metal ͑SIN͒ tunnel junctions are formed between Bi-2212 crystals and a Au tip, which display well-resolved quasiparticle gap features including sharp conductance peaks. Reproducible superconductor-insulator-superconductor ͑SIS͒ tunnel junctions are also obtained between two pieces of the Bi-2212 crystals, resulting in simultaneous quasiparticle and Josephson currents. The dynamic conductances of both SIN and SIS junctions are qualitatively similar to those found on optimally doped Bi-2212, but with reduced gap values, e.g., ⌬ϭ15-20 meV for T c ϭ62 K. Fits to the conductance data in the gap region are obtained using a model with d x 2 Ϫy 2 symmetry, and it is shown that this provides a better fit than s-wave symmetry. Both SIN and SIS tunneling conductances also display dip and hump features at high bias voltages similar to those found on optimal and underdoped crystals, indicating that these are intrinsic properties of the quasiparticles. The SIS data indicate that these features appear to be part of a larger spectrum that extends out to 300-400 mV. The Josephson current has been measured for 13 SIS junctions on the 62 K crystals with resistances varying over two decades. It is found that the maximum value depends on junction resistance in a manner consistent with Ambegaokar-Baratoff theory, but with a reduced I c R n product.

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Section: Introductionsupporting

confidence: 52%

Quasiparticle and Josephson tunneling of overdopedBi2Sr2CaCu2<

2000

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“…These experiments can be devided into those probing the amplitude by studying the quasiparticle excitation spectrum and those probing the phase of the order parameter in interferometer experiments employing multiply connected superconductors. Certainly, the key experiments have been the phase sensitive experiments designed by Tsuei and Kirtley which employ HTS thin film tricrystals [3,4]. In these experiments a scanning SQUID-system has been used to show that there are half-integer flux quanta in superconducting rings formed by three differently oriented HTS grains connected by grain boundary Josephson junctions.…”

Section: Introductionmentioning

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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“…We consider mixed symmetries, including a small isotropic component to the d-waves, such that the magnitude and phase of the pair potential are affected [39][40][41].…”

Section: Resultsmentioning

confidence: 99%

“…For this, we use the Hamiltonian approach and the non-equilibrium Green functions in Keldysh formalism. We consider typical pair potential symmetries for cuprates and iron based superconductors which means d, s ++ and s +− symmetries [39][40][41][42][43][44][45][46]. In addition, we consider a s-wave compound added to the d-wave superconductors, thus we study how the magnitude and phase of the pair potential affect the noise cross-correlation.…”

Section: Introductionmentioning

confidence: 99%

Noise cross-correlation and Cooper pair splitting efficiency in multi-teminal superconductor junctions

Gil

Herrera

2017

Solid State Communications

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We analyze the non-local shot noise in a multi-terminal junction formed by two Normal metal leads connected to one superconductor. Using the cross Fano factor and the shot noise, we calculate the efficiency of the Cooper pair splitting. The method is applied to d-wave and iron based superconductors. We determine that the contributions to the noise cross-correlation are due to crossed Andreev reflections (CAR), elastic cotunneling, quasiparticles transmission and local Andreev reflections. In the tunneling limit, the CAR contribute positively to the noise cross-correlation whereas the other processes contribute negatively. Depending on the pair potential symmetry, the CAR are the dominant processes, giving as a result a high efficiency for Cooper pair split. We propose the use of the Fano factor to test the efficiency of a Cooper pair splitter device.

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Symmetry of the order parameter in the high-Tc superconductor YBa2Cu3O7- δ

Cited by 343 publications

References 17 publications

Quasiparticle and Josephson tunneling of overdopedBi2Sr2CaCu2<

Quasiparticle and Josephson tunneling of overdopedBi2Sr2CaCu2<

Andreev bound states in high temperature superconductors

Noise cross-correlation and Cooper pair splitting efficiency in multi-teminal superconductor junctions

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