Ru transition metal oxide Sr2RuO4, with the perovskite crystal structure, show novel spin-triplet superconductivity with Tc=1.4K.
The symmetry of Cooper pairs and the origin of superconductivity are not still clarified.
 
       
 
Several experiments suggest that the superconducting state of this material has the horizontal node. The spin-fluctuation mechanism originated from the on-site Coulomb interaction cannot explain the horizontal node, as shown from the perturbative calculations. We have proposed a new mechanism of spin-triplet superconductivity with the horizontal line node. In our model the inter-band interaction between three orbitals dxy, dyz, dzx play an important role to exhibit a novel superconductivity.
 
   
Superconductivity from the Coulomb Scattering Mechanism

The superconducting gap has horizontal nodes as shown in the figure.

Ref. S. Koikegami et al.: Physical Review B67, 134517 (2003).
 
 
  Condensed Matter Physics Group: Nanoelectronics Research Institute