Point-contact electron tunneling into the high-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>superconductor Y-Ba-Cu-O

Kirk,; Dp, Smith; Mitzi, D. B.; Jz, Sun; Webb, DJ; Char, K.; Mr, Hahn; Naito, Makio; Oh, Byeong Yun; Mr, Beasley; Th, Geballe; Rh, Hammond; Kapitulnik, A.; Cf, Quate

doi:10.1103/physrevb.35.8850

Cited by 81 publications

(5 citation statements)

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“…For superconductors, PCS provides a quantitative measure of Andreev reflection and helps determine the superconducting order parameters and the paring mechanism [6,7]. Especially, a universal asymmetry has been observed in the point contact tunneling experiments of high T C superconductors [8], in contrast to what is expected for Bardeen-Cooper-Schrieffer type superconductors.…”

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Fano effect in the point contact spectroscopy of heavy-electron materials

Yang

2009

Phys. Rev. B

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We show that Fano interference explains how point contact spectroscopy in heavy-electron materials probes the emergence of the Kondo heavy-electron liquid below the same characteristic temperature T ‫ء‬ as that seen in many other experiments and why the resulting measured conductance asymmetry reflects the universal Kondo liquid behavior seen in these. Its physical origin is the opening of a new channel for electron tunneling beyond that available from the background conduction electrons. We derive the Fano formula with a mean-field slave boson approach for the Kondo lattice model and generalize it to finite temperature and realistic situation by introducing empirical parameters. The resulting simple expression for the Fano interference provides a good fit to the experimental results for CeCoIn 5 , CeRhIn 5 , and YbAl 3 , over the entire range of bias voltages, and deduce a lifetime of the heavy quasiparticle excitations that agrees well with recent state-of-the-art numerical calculations.Heavy-electron materials have a rich phase diagram showing a competition between antiferromagnetism and unconventional superconductivity and quantum critical behavior. Although the underlying physics responsible for this competition is still unclear, it appears to be primarily associated with the heavy electron, or Kondo liquid, that emerges from the collective hybridization of light conduction electrons with the local f moments. 1-4 Understanding the nature and consequence of this hybridization is therefore a central task in the field of heavy-electron physics.Point contact spectroscopy ͑PCS͒ ͑Ref. 5͒ probes the lowenergy collective excitations ͑such as phonons͒ and may be expected to provide important information for our understanding of the low-energy physics of heavy-electron materials. For superconductors, PCS provides a quantitative measure of the Andreev reflection and helps determine the superconducting order parameters and the paring mechanism. 6 Especially, a universal asymmetry has been observed in the point contact tunneling experiments of high-T C superconductors, 7 in contrast to what is expected for Bardeen-Cooper-Schrieffer-type superconductors.For decades, a similar conductance asymmetry has also been observed in many heavy-electron materials such as CeCu 6 ͑Ref. 8͒ and URu 2 Si 2 ͑Ref. 9͒ but its origin has not been understood. For example, the fact that the asymmetry is practically independent of the material of the metallic tips suggests that it is intrinsic and excludes previous explanations based on self-heating effects. 10 On the other hand, the usual tunneling model requires an unrealistic background density of states ͑DOS͒ to explain the experimental data. In CeCoIn 5 , the DOS derived from it has a broad maximum below the Fermi energy, 11 in contradiction with the theoretical expectations and numerical calculations that show a sharp quasiparticle peak developing at low temperatures well above the Fermi energy.An essential clue to the underlying physics comes from two recent observations concerning the p...

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confidence: 99%

Fano effect in the point contact spectroscopy of heavy-electron materials

Yang

2009

Phys. Rev. B

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“…10). Most of the tunneling sturlies on YBaCuO which show interesting gap-like features have used small area point contacts to fabricate the tunnel junction [73,74,75,76]. In all these experiments normal conductor tips were used as counter electrodes.…”

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Epitaxial growth and properties of YBaCuO thin films

Geerk

Linker

Meyer

1989

Materials Science Reports

180

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The growth quality ofYBaCuO thin films deposited by sputtering on different substrates (AlzOs, MgO, SrTiOs, Zr(Y)Oz) has been studied by X-ray diffraction and channeling experiments as a function ofthe deposition temperature. Besides the substrate orientation, the substrate temperature is the parameter determining whether films grow in c-, a-, (110) or mixed directions. Epitaxial growth correlates with high critical current values in the films ofup to 5.5 x 106 AJcm2 at 77 K. Ultrathin films with thicknesses down to 2 nm were grown revealing threedimensional superconducting behaviour. Films on (100) SrTiOs of9 nm thickness and below are partially strained indicating commensurate growth. From the analysis of the surface disorder 1 displaced Ba atom per Baz Y row was obtained indicating that the disordered layer thickness is about 0.6 nm. Tunnel junctions fabricated on these films reveal gap-like structures near ±16m V and ±30m V.Epitaktisches Wachsturn und Eigenschaften dünner Schichten des Hochtemperatur-Supraleiters YBaCuO ZUSAMMENFASSUNG Das Verfahren der Magnetron-Kathodenzerstäubung wurde zur Abscheidung dünner YBaCuO-Schichten auf verschiedenen Substraten (AlzOs, MgO, SrTiOs, Zr(Y)Oz) optimiert. Die Wachstumsrichtung und die kristalline Güte der Schichten wurde in Abhängigkeit von der Substrat-Oberflächengüte, der Orientierung und der Temperatur mittels Ionenchanneling und Röntgendiffraktion untersucht. Der Grad der Epitaxie und die Mosaik-Verbreiterung bestimmen den kritischen Transportstrom mit Werten bis zu 5.5 ·106 Ä/cm2 bei 77 K. Selbst in ultradünnen Schichten mit einer minimalen Dicke von bis zu 2 nm zeigt das supraleitende Verhalten 3-dimensionalen Charakter. Schichten auf (100) SrTiOs mit Dicken kleiner etwa 9 nm sind teilweise zur Unterlage verspannt, was auf kommensurables Wachstum hinweist. Die Channeling-Analyse der Schichtoberfläche ergibt in günstigen Fällen eine Verlagerung von nur 1 Ba-Atom pro Baz YKette, was einer maximalen Dicke der gestörten Oberfläche von etwa 0.6 nm entspricht. Auf diesen Schichten präparierte Tunneldioden zeigen Strukturen mit einer Energielücke inderNähe von ±16m V und ±30m V.--I --

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“…The gaplike structure in scanning tunneling microspectroscopy ͑STM͒, though frequently inferred to be evidence of superconductivity, [1][2][3] could also be a manifestation of singleelectron charging ͑SEC͒ effects. [4][5][6][7] It has been demonstrated 5 that, in a typical SEC system, the multiple-peak tunneling features similar to those observed in high-T C superconductors ͑HTS's͒ were unambiguously reproduced.…”

Section: ͓S0163-1829͑98͒09841-5͔mentioning

confidence: 99%