Midgap state-based π-junctions for digital applications

Testa, Gianluca; Monaco, A.; Esposito, E.; Sarnelli, E.; Kang, Dae Joon; Mennema, S. H.; Tarte, E.J.; Blamire, M. G.

doi:10.1063/1.1781744

Cited by 35 publications

(36 citation statements)

References 20 publications

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“…The first studies on bicrystal submicron JJs have given encouraging results as the reduction of decoherence [53], the presence of the 2ϕ component [54], and of Andreev bound states [55].…”

Section: Mesoscopic Effects and Coherence In Hts Nanostructuresmentioning

confidence: 99%

Macroscopic quantum phenomena in Josephson structures

Barone

Lombardi

Rotoli³

et al. 2010

Low Temperature Physics

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The Josephson effect is a probe of unparalleled performances in the study of a variety of macroscopic quantum phenomena. In the present article an overview of important achievements and challenging trends is given referring, in particular, to macroscopic quantum tunneling and energy level quantization. The attention is mainly addressed to high-C T superconducting structures and recent investigations concerning nanostructures.

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“…The first studies on bicrystal submicron JJs have given encouraging results as the reduction of decoherence [53], the presence of the 2ϕ component [54], and of Andreev bound states [55].…”

Section: Mesoscopic Effects and Coherence In Hts Nanostructuresmentioning

confidence: 99%

Macroscopic quantum phenomena in Josephson structures

Barone

Lombardi

Rotoli³

et al. 2010

Low Temperature Physics

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“…In fact, along with PCARS, the Josephson effect has been used in the past as a probe of electronic properties in superconductors, included the order parameter symmetry (e.g. [14][15][16][17]). In this paper, in order to discriminate between different symmetries of the order parameter (s ++ and s ± ), we develop a quantum waveguides approach for the Josephson effect in a multiband superconducting junction.…”

Section: Introductionmentioning

confidence: 99%

Quantum waveguide theory of the Josephson effect in multiband superconductors

et al. 2015

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We formulate a quantum waveguide theory of the Josephson effect in multiband superconductors, with special emphasis on iron-based materials. By generalizing the boundary conditions of the scattering problem, we first determine the Andreev levels spectrum and then derive an explicit expression for the Josephson current which generalizes the formula of the single band case. In deriving the results, we provide a second quantization field theory allowing to evaluate the currentphase relation and the Josephson current fluctuations in multiband systems. We present results for two different order parameter symmetries, namely s± and s++, which are relevant in multiband systems. The obtained results show that the s± symmetry can support π states which are absent in the s++ case. We also argue a certain fragility of the Josephson current against phase fluctuations in the s++ case. The temperature dependence of the Josephson critical current is also analyzed and we find, for both the order parameter symmetries, remarkable violations of the Ambegaokar-Baratoff relation. The results are relevant in view of possible experiments aimed at investigating the order parameter symmetry of multiband superconductors using mesoscopic Josephson junctions.

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“…3,5. Stimulated by this theory, extensive studies of MARS in unconventional superconductor junctions have been performed during the last decade: in the case of broken time reversal symmetry state [21][22][23][24][25][26][27][28], in triplet superconductor junctions [29][30][31][32][33][34], in quasi-one-dimensional organic superconductors [35][36][37][38], MARS and Doppler effect [39][40][41][42][43], MARS in ferromagnetic junctions [44][45][46][47][48][49][50][51][52], influence of MARS on Josephson effect [53][54][55][56][57][58][59][60][61][62], and other related problems [63][64][65][66]…”

Section: Introductionmentioning

confidence: 99%

Impurity scattering effect on charge transport in high-Tc cuprate junctions

Tanaka

Asano

Kashiwaya

2004

Low Temperature Physics

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It is known that the zero-bias conductance peak (ZBCP) is expected in tunneling spectra of normal-metal/high-T c cuprate junctions because of the formation of the midgap Andreev resonant states (MARS) at junction interfaces. In the present review, we report the recent theoretical study of impurity scattering effects on the tunneling spectroscopy. In the former part of the present paper, we discuss impurity effects in normal metal. We calculate tunneling conductance for diffusive normal metal (DN)/high T c cuprate junctions based on the Keldysh Green's function technique. Besides the ZBCP due to the MARS, we can expect ZBCP caused by the different origin, i.e., the coherent Andreev reflection (CAR) assisted by the proximity effect in DN. Their relative importance depends on the angle a between the interface normal and the crystal axis of high-T c superconductors. At a = 0, we find the ZBCP by the CAR for low transparent junctions with small Thouless energies in DN; this is similar to the case of diffusive normal metal/insulator/s-wave superconductor junctions. Under increase of a from zero to p/4, the contribution of MARS to ZBCP becomes more prominent and the effect of the CAR is gradually suppressed. Such complex spectral features would be observable in conductance spectra of high-T c junctions at very low temperatures. In the latter part of our paper, we study impurity effects in superconductors. We consider impurities near the junction interface on the superconductor side. The conductance is calculated from the Andreev and the normal reflection coefficients which are estimated by using the single-site approximation in an analytic calculation and by the recursive Green function method in a numerical simulation. We find splitting of the ZBCP in the presence of the time reversal symmetry. Thus the zero-field splitting of ZBCP in the experiment does not perfectly prove an existence of broken time reversal symmetry state.

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Midgap state-based π-junctions for digital applications

Abstract: Fabrication of high-temperature superconductor Josephson junctions by focused ion beam milling

Cited by 35 publications

References 20 publications

Macroscopic quantum phenomena in Josephson structures

Macroscopic quantum phenomena in Josephson structures

Quantum waveguide theory of the Josephson effect in multiband superconductors

Impurity scattering effect on charge transport in high-Tc cuprate junctions

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