0 Large oxygen - isotope effect in Sr 0 . 4 K 0 . 6 BiO 3 : Evidence for phonon - mediated superconductivity
نویسنده
چکیده
Oxygen-isotope effect has been investigated in a recently discovered superconductor Sr0.4K0.6BiO3. This compound has a distorted perovskite structure and becomes superconducting at about 12 K. Upon replacing 16O with 18O by 60-80%, the Tc of the sample is shifted down by 0.32-0.50 K, corresponding to an isotope exponent of αO = 0.40(5). This isotope exponent is very close to that for a similar bismuthate superconductor Ba1−xKxBiO3 with Tc = 30 K. The very distinctive doping and Tc dependencies of αO observed in bismuthates and cuprates suggest that bismuthates should belong to conventional phonon-mediated superconductors while cuprates might be unconventional supercondutors.
منابع مشابه
Isotope Effect on m∗ in High-Tc Materials due to the Breakdown of Migdal’s Theorem
– We show that the inclusion of effects beyond Migdal’s limit in the electron-phonon interaction naturally leads to an isotope effect for the effective mass m∗ of the charge carriers even much before reaching the polaron limit. This is the situation already considered in our approach to nonadiabatic superconductivity [7]. Such a result provides a scenario different from the polaronic one for th...
متن کاملThe reduced total isotope effect and its implications on the nature of superconductivity in MgB2
The recent discovery of superconductivity at ~39 K in MgB2, by Nagamatsu et al.1 establishes this simple binary compound as having the highest bulk superconducting transition temperature, Tc, of any non-copper-oxide material. Much of the initial research has focused on whether MgB2 is a conventional BCS, electron-phonon mediated superconductor, and, if it is, why Tc is so high. Isotope effect m...
متن کاملThe Imaginary Part of the Optical Conductivity of Ba 1 − x K x BiO
The frequency dependence of the imaginary part of the infrared conductivity is calculated for a superconductor. Sharp structure, characteristic of superconductivity with an order parameter with s-wave symmetry, appears in the BCS limit as a minimum at a frequency equal to twice the gap value. This structure scales with temperature but gets progressively smeared and shifted as impurity scatterin...
متن کاملIntrinsic and structural isotope effects in iron-based superconductors
The currently available results of the isotope effect on the superconducting transition temperature Tc in Fe-based high-temperature superconductors (HTSs) are highly controversial. The values of the Fe isotope effect exponent �Fe for various families of Fe-based HTS were found to be as well positive, as negative, or even be exceedingly larger than the BCS value �BCS�0.5. Here we emphasize that ...
متن کاملCalculated elastic and electronic properties of MgB 2 at high pressures
The effect of high pressure on structural and electronic properties of the novel super-conductor MgB 2 has been calculated using the full-potential linearized augmented-plane-wave method. Despite the layered crystal structure of MgB 2 nearly isotropic compression (bulk modulus B 0 = 140.1(6) GPa) is found with only a 1.2% decrease of the c/a ratio at 10 GPa. The effect of pressure on the critic...
متن کامل