The low-temperature specific heat (SH) of overdoped La2-x Srx Cu O4 single crystals (0.178≤x≤0.290) has been measured. For the superconducting samples (0.178≤x≤0.238), the derived gap values (without any adjusting parameters) approach closely onto the theoretical prediction Δ0 =2.14 kB Tc for the weak-coupling d -wave BCS superconductivity. In addition, the residual term γ (0) of SH at H=0 increases with x dramatically when beyond x∼0.22, and finally evolves into the value of a complete normal metallic state at higher doping levels, indicating a growing amount of unpaired electrons. We argue that this large γ (0) cannot be simply attributed to the pair breaking induced by the impurity scattering, instead the phase separation is possible.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2007 Aug 10|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics