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  • 1
    Electronic Resource
    Electronic Resource
    Tunneling investigations of the phonon spectrum of a Bi 2223 metal oxide at high pressures (1997)
    Springer
    Physics of the solid state 39 (1997), S. 1572-1574 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Pronounced softening of the high-frequency part of the phonon spectrum at high pressures is observed by means of tunneling spectroscopy. As the pressure is increased, the characteristic frequencies of the spectrum at ħΩ〉60 mV decrease at the rate d ln(ħΩ)/dP≈(−6.5±0.5)×10−3 kbar−1. On the other hand, hydrostatic pressure causes the low frequencies of the phonon spectrum of Bi 2223 metal oxide to shift very slightly toward higher energies, consistent with Raman spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1129900
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  • 2
    Electronic Resource
    Electronic Resource
    Temperature dependence of the energy gap in Bi2223 metal oxide superconductor (2000)
    Springer
    JETP letters 71 (2000), S. 289-292 
    Details
    ISSN: 1090-6487
    Keywords: 74.20.−z ; 74.50.+r
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spectroscopic studies of the silver-optimum-doped Bi2223 contacts show that the temperature dependence of the parameter Δ follows the BCS curve. However, the tunnel measurements performed for the same series of specimens did not reveal any temperature dependence of the energy gap Δ. The feature observed in the tunnel density of states was retained at temperatures T〉T c , manifesting the presence of the temperature-independent pseudogap E p . The difference between the data obtained with tunnel spectroscopy and Andreev reflection spectroscopy is explained by the fact that the latter measures the true superconducting energy gap Δs(T), whereas the peaks of the tunneling conductivity are related to the total energy gap Δ of cuprates, which includes both the parameter Δs and the pseudogap $$E_p :\Delta \approx \sqrt {\Delta _s^2 + E_p^2 } $$ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.568336
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  • 3
    Electronic Resource
    Electronic Resource
    Spectroscopy of quasiparticle excitations of superconducting bismuth cuprate at high pressures (1998)
    Springer
    Journal of experimental and theoretical physics 86 (1998), S. 763-770 
    Details
    ISSN: 1090-6509
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study the energy spectrum of Bi2223 (Bi1.6Pb0.4Sr1.8Ca2.2Cu3Ox) at high hydrostatic pressures by Andreev-and tunneling-spectroscopy methods. We determine the gap anisotropy in the basal ab plane and find the following values for the parameters Δ(ϕ): Δmax=42 mV, and Δmin=19.5 mV (T c =110 K and dT c /dP=0.16 K/kbar). We detect an increase in the ratio R=2Δmax/kT c with pressure P; for Bi2223 cuprate, dR/dP≈0.017 kbar−1. In the phonon-frequency region we detect a “softening,” due to pressure, of the high-frequency part of the phonon spectrum corresponding to “breathing” modes of oxygen, as well as other optical modes of Cu-O. The characteristic frequencies of the spectrum for ℏΩ〉60 mV are found to decrease, with increasing pressure, at a rate d ln(ℏΩ)/dP≈−6.5±0.5×10−3 kbar−1. This result explains the observed increase in the ratio 2Δ/kT c (P) in the model of strong electron-phonon interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.558537
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  • 4
    Electronic Resource
    Electronic Resource
    Spin-polarized electron tunneling in lanthanum manganite (2000)
    Springer
    Journal of experimental and theoretical physics 91 (2000), S. 547-552 
    Details
    ISSN: 1090-6509
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Tunneling experiments were performed on ceramic samples with the composition La0.6Sr0.4MnO3, manifesting negative magnetoresistance. Two types of contacts were studied: symmetric (break junction type) and asymmetric ceramic-insulator-metal contact. A high magnetic-field sensitivity of the conductivity σ(H) of the contacts was observed even when only one of the electrodes was magnetic. The effect was explained by the existence of spin-polarized localized states in the tunneling barrier. Their appearance was attributed to the formation of an oxygen-depleted, magnetically two-phase state of localized ferromagnetic nanoregions in an anti-ferromagnetic dielectric matrix in the near-contact region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1320090
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  • 5
    Electronic Resource
    Electronic Resource
    Resistive vortices and two-dimensional transition in aluminum films (1984)
    Springer
    Journal of low temperature physics 57 (1984), S. 619-627 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Thermally excited fluxoids are found in the resistive region of the superconducting transition of thin aluminum films withR ▭=10 Ω by a method using a dc transformer. TheR(T) andI–V dependences obtained atT→T 2D correspond to the universal relations of the theory of a Berezinskii-Kosterlitz-Thouless phase transition. The observed effects are related to the presence of a two-dimensional system of Josephson weak links in the films and the dissipative dynamics of the fluxoids in such structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683685
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    Paper (German National Licenses)
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