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  • Articles  (6)
  • isotope effect  (6)
  • Springer  (6)
  • Nature Publishing Group
  • 2020-2023
  • 2005-2009
  • 2000-2004  (6)
  • 1975-1979
  • Electrical Engineering, Measurement and Control Technology  (6)
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  • Articles  (6)
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  • Springer  (6)
  • Nature Publishing Group
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  • 1
    Electronic Resource
    Electronic Resource
    Doping and Isotope Dependence of the Pseudogap in High-Tc Cuprates Observed by Neutron Crystal-Field Spectroscopy: A Fast Local Probe (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 727-730 
    Details
    ISSN: 1572-9605
    Keywords: doping ; isotope effect ; pseudogap ; high-T c cuprates ; crystal-field spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The temperature dependence of the relaxation rate of crystal-field excitations in the high-T c superconductors HoBa2Cu4O8 and HoBa2Cu3O x (6.4 〈 x 〈 7) was investigated by inelastic neutron scattering techniques. The data show clear evidence for the opening of an electronic gap in the normal state at T* 〉 T c in the underdoped regime as well as for slightly overdoped samples. For HoBa2Cu4O8 T* increases from 170 to 220 K upon oxygen isotope substitution (16O vs 18O). This huge isotope shift (which is absent in NMR and NQR experiments) suggests that the mechanism leading to an isotope effect on the pseudogap has to involve a time scale in the range 10−8 ≫ τ 〉 10−13 s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007806029650
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  • 2
    Electronic Resource
    Electronic Resource
    Tilting Mode Relaxation and Oxygen Isotope Effect in La2−xSrxCuO4 Studied by Electron Paramagnetic Resonance (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 955-958 
    Details
    ISSN: 1572-9605
    Keywords: EPR ; LSCD ; isotope effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The electron paramegnetic resonance (EPR) of Mn2+ doped into La2−x Sr x CuO4 was used to probe the copper spin relaxation via the bottleneck effect for oxygen isotope (16O and 18O)–substituted samples. It was found that the EPR linewidth is larger for the 18O isotope samples than for the 16O samples. For x = 0.03, the linewidth for the 18O sample is larger than for 16O sample by a factor of 2. The isotope effect is pronounced at low temperatures and decreases with increasing Sr concentration. This effect is quantitatively explained by the Cu2+ S = 1/2 spin relaxation to the lattice via Dzyaloshinski terms coupled linearly to the local Q 4/Q 5 tilting modes of the CuO6 octahedra as proposed by Kochelaev et al. [1] The Q 4/Q 5 modes are coupled sterically to the Q 2 Jahn–Teller modes considered to be relevant for the (bi)-polaron formation and thus for the high-temperature superconductivity (HTSC).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026498123890
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  • 3
    Electronic Resource
    Electronic Resource
    Doping Dependence of the Effective Mass Anisotropy and Oxygen-Isotope Effect on the Magnetic Penetration Depth: The Role of Lattice Vibrations in High-Temperature Superconductivity (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 963-969 
    Details
    ISSN: 1572-9605
    Keywords: phase diagram ; critical fluctuations ; isotope effect ; polarons ; magnetic torque
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Studies of the critical behavior of high-temperature superconductors (HTSC) show the importance of the strong doping dependence of the effective mass anisotropy γ for the generic (T, x) phase diagram of these materials. A possible microscopic model that can explain the doping dependence of γ is based on polaronic charge carriers. That lattice effects may play a role for high-temperature superconductivity is further supported by measurements of the oxygen-isotope effect on the in-plane penetration depth λ ab (0) in underdoped La2−x Sr x CuO4 single crystals that are reported in this paper. The oxygen-isotope effect on λ−2 ab (0) is found to be around −9% for the samples investigated. It arises mainly from the oxygen–mass dependence of the in-plane effective mass m* ab . The experimental facts presented in this paper suggest that lattice vibrations are important for the occurrence of high-temperature superconductivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026402324799
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  • 4
    Electronic Resource
    Electronic Resource
    Plasmon–Phonon Pairing Mechanism and Superconducting State Parameters in Layered Mercury Cuprates (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 593-601 
    Details
    ISSN: 1572-9605
    Keywords: pairing mechanism ; transition temperature ; isotope effect ; cuprates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An effective two-dimensional dynamic interaction is developed which incorporates screening of holes by plasmons and by optical phonons to discuss the nature of the pairing mechanism leading to superconductivity in layered mercury cuprates. The system is treated as an ionic solid containing layers of charge carriers and a model dielectric function is set up which fulfils the appropriate sum rules on the electronic and ionic polarizabilities. The static limit of the model dielectric function is used to calculate the effective hole-hole coupling strength. The values of the electron-phonon coupling strength and of the Coulomb interaction parameter indicate that the superconductor is in the strong coupling regime with effective screening of the charge carriers. The superconducting transition temperature of optimally doped HgBa2CuO4+δ is estimated as 120 K from Kresin's strong coupling theory and the energy gap ratio is substantially larger than the BCS value. The value of the isotope exponent is severely reduced below the BCS value. The implications of the model and its analysis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007829018708
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  • 5
    Electronic Resource
    Electronic Resource
    Isotope Effect on Properties of CMR Manganites (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 305-312 
    Details
    ISSN: 1572-9605
    Keywords: manganites ; CMR ; isotope effect ; electron-phonon interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A unique feature of incredibly large magnetoresistance and also the properties, in which electronlattice interactions play a key role, has attracted a lot of attention to manganese oxides. Oxygen isotope effect has proved to be spectacular in this system and it gives insight into many characteristics of interactions and charge transfer in this system. This review concentrates on transformation of properties induced by oxygen 16O–18O isotope substitution and mechanisms leading to this extraordinary effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007764403181
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  • 6
    Electronic Resource
    Electronic Resource
    Phase Separation in a Two-Component Model for Cuprates (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 765-769 
    Details
    ISSN: 1572-9605
    Keywords: two-component model ; phase separation ; Jahn–Teller effect ; hybridization ; isotope effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In a brief review the role of interactions in a two-component model for electronic spectrum in cuprates is discussed. Interactions in the model result in a tendency to phase separation. It is speculated that the latter determines the scale of the “pseudogap” temperature, T*, while hybridization between localized and itinerant components moderates this tendency to the first-order transition and brings about isotope mass dependence through polaronic effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007874418264
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