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Suppression of superconductivity in granular metals
I S Beloborodov1, A V Lopatin, V M Vinokur
1Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
Physical Review Letters
|June 1, 2004
Summary
We studied how Coulomb repulsion affects superconductivity in granular metals. At high conductance, granular samples show insulating, superconducting, or a unique metallic phase where superconductivity is suppressed.
Area of Science:
- Condensed Matter Physics
- Materials Science
Background:
- Granular metallic systems exhibit complex electronic properties.
- Superconducting transition temperature (SC T_c) can be influenced by intergrain interactions.
Purpose of the Study:
- Investigate the suppression of SC T_c in granular metals due to Coulomb repulsion.
- Analyze systems with large tunneling conductance between grains (g(T)>>1).
Main Methods:
- Theoretical analysis of superconducting transition temperature corrections.
- Examination of 3D granular samples and thin films.
Main Results:
- Identified two distinct groups of granular samples based on their properties.
- Group (i) exhibits insulating or superconducting states at zero temperature, dependent on intergranular conductance.
- Group (ii) displays an intermediate metallic phase with suppressed superconductivity and weak Coulomb blockade effects.
Conclusions:
- Coulomb repulsion significantly impacts SC T_c in granular metals.
- The interplay between intergranular conductance and Coulomb effects dictates the electronic state (insulating, metallic, or superconducting).
- Discovery of an intermediate metallic phase offers new insights into granular electronic systems.