Observation of Two Distinct Superconducting Phases in CeCu2Si2
H. Q. Yuan,1,2*
F. M. Grosche,3
M. Deppe,1
C. Geibel,1
G. Sparn,1
F. Steglich1
We report the presence of two disconnected superconducting domes
in the pressure-temperature phase diagram of partially germanium-substituted
CeCu
2Si
2. The lower density superconducting dome lies on the
threshold of antiferromagnetic order, indicating magnetically
mediated pairing, whereas the higher density superconducting
regime straddles a weakly first-order volume collapse, suggesting
a pairing interaction based on spatially extended density fluctuations.
Two distinct pairing mechanisms thus appear to operate in the
single, wide, superconducting range of stoichiometric CeCu
2Si
2,
both of which might apply more generally to other classes of
correlated electron systems.
2 Department of Physics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China.
3 Department of Physics, Royal Holloway, University of London, Egham TW20 0EX, UK.
* To whom correspondence should be addressed. E-mail: yuan{at}cpfs.mpg.de
