Resonant transport through midgap states in voltage-biased Josephson junctions of d-wave superconductors

Löfwander, Tomas; Johansson, Göran; Shumeiko, Vitaly; Wendin, Göran; Hurd, Magnus

doi:10.1006/spmi.1999.0745

Cited by 6 publications

(1 citation statement)

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“…In d-wave superconductors, the subgap structure (Hurd 1997, Hurd et al 1999, Löfwander et al 1999a, b, Samanta and Datta 1998, Yoshida et al 1999 is very different for two reasons: (1) the multiparticle current thresholds are washed out due to the gap nodes, (2) the presence of MGS changes the resonances in energy space. For the d 0 /d 0 orientation (no MGS in the junction), the single-particle current dominates the I -V characteristics because of the gap nodes.…”

Section: Theoretical Formulationmentioning

confidence: 99%

Andreev bound states in high-T_csuperconducting junctions

Löfwander

Shumeiko

Wendin

2001

Supercond. Sci. Technol.

296

300

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The formation of bound states at surfaces of materials with an energy gap in the bulk electron spectrum is a well known physical phenomenon. At superconductor surfaces, quasiparticles with energies inside the superconducting gap may be trapped in bound states in quantum wells, formed by total reflection against the vacuum and total Andreev reflection against the superconductor. Since an electron reflects as a hole and sends a Cooper pair into the superconductor, the surface states give rise to resonant transport of quasiparticle and Cooper pair currents, and may be observed in tunnelling spectra. In superconducting junctions these surface states may hybridize and form bound Andreev states, trapped between the superconducting electrodes. In d-wave superconductors, the order parameter changes sign under 90 • rotation and, as a consequence, Andreev reflection may lead to the formation of zero energy quasiparticle bound states, midgap states (MGS). The formation of MGS is a robust feature of d-wave superconductivity and provides a unified framework for many important effects which will be reviewed: large Josephson current, low-temperature anomaly of the critical Josephson current, π -junction behaviour, 0 → π junction crossover with temperature, zero-bias conductance peaks, paramagnetic currents, time reversal symmetry breaking, spontaneous interface currents, and resonance features in subgap currents. Taken together these effects, when observed in experiments, provide proof for d-wave superconductivity in the cuprates.

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Section: Theoretical Formulationmentioning

confidence: 99%

Andreev bound states in high-T_csuperconducting junctions

Löfwander

Shumeiko

Wendin

2001

Supercond. Sci. Technol.

296

300

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Multiple Andreev reflections as a transport problem in energy space

Johansson

Wendin

Bratus

et al. 1999

Superlattices and Microstructures

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We present an approach for analyzing the dc current in voltage biased quantum superconducting junctions. By separating terms from different $n$-particle processes, we find that the $n$-particle current can be mapped on the problem of wave transport through a potential structure with $n$ barriers. We discuss the relation between resonances in such structures and the subgap structures in the current-voltage characteristics. At zero temperature we find, exactly, that only processes creating real excitations contribute to the current. Our results are valid for a general SXS-junction, where the X-region is an arbitrary non-superconducting region described by an energy-dependent transfer matrix.Comment: 11 pages, 4 figures, submitted to Superlattices and Microstructure

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