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Reentrant superconducting phase in conical-ferromagnet-superconductor nanostructures
Chien-Te Wu1, Oriol T Valls, Klaus Halterman
1School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA. wu@physics.umn.edu
Physical Review Letters
|May 1, 2012
Summary
Superconductivity can reenter at low temperatures in a superconductor-magnet bilayer. This reentrant behavior, where superconductivity reappears upon cooling, is observed in specific magnetic layer thicknesses.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Superconductivity
Background:
- Investigating bilayers composed of superconductors and magnets is crucial for understanding exotic electronic states.
- Spiral magnetic structures, like the Ho type, introduce complex magnetic interactions that can influence superconductivity.
Purpose of the Study:
- To explore the phenomenon of reentrant superconductivity in a bilayer system comprising an ordinary superconductor and a magnet with a Ho-type spiral magnetic structure.
- To analyze the impact of magnetic layer thickness on superconducting properties.
Main Methods:
- Utilizing a self-consistent solution of the Bogoliubov-de Gennes equations.
- Evaluating key superconducting parameters: pair amplitude, transition temperature, free energy, and entropy.
Main Results:
- Observed reentrant superconductivity as a function of temperature for specific magnetic layer thicknesses.
- Demonstrated that both condensation free energy and pair potential vanish at the upper and lower transition temperatures.
- Identified a temperature range where the superconducting state exhibits higher entropy (less order) than the normal state.
Conclusions:
- The study confirms strictly reentrant superconductivity, where the low and high-temperature superconducting phases are identical.
- The findings highlight the intricate interplay between magnetism and superconductivity in layered materials.
- Entropy analysis provides further insight into the thermodynamic stability and ordering of the superconducting state.
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