Prozorov R, Giannetta RW, Fournier P, Greene RL
Loomis Laboratory of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801, USA.
Phys Rev Lett. 2000 Oct 23;85(17):3700-3. doi: 10.1103/PhysRevLett.85.3700.
The in-plane magnetic penetration depth, lambda(T), was measured down to 0.4 K in single crystals of electron-doped superconductors, Pr(1.85)Ce(0.15)CuO(4-delta) (PCCO) and Nd(1.85)Ce(0.15)CuO(4-delta) (NCCO). In PCCO, the superfluid density varies as T2 from 0.025 up to roughly 0.3T/T(c) suggestive of a d-wave state with impurities. In NCCO, lambda(T) shows a pronounced upturn for T<4 K due to the paramagnetic contribution of Nd3+ ions. Fits to an s-wave order parameter over the standard BCS range (T/T(c) = 0.32) limit any gap to less than Delta(min)(0)/T(c) = 0.57 in NCCO. For PCCO, the absence of paramagnetism permits a lower temperature fit and yields an upper limit of Delta(min)(0)/T(c) = 0.2.
在电子掺杂超导体Pr(1.85)Ce(0.15)CuO(4-δ)（PCCO）和Nd(1.85)Ce(0.15)CuO(4-δ)（NCCO）的单晶中，测量了面内磁穿透深度λ(T)，测量温度低至0.4 K。在PCCO中，超流密度从0.025到大约0.3T/Tc随T2变化，这表明存在杂质的d波态。在NCCO中，由于Nd3+离子的顺磁贡献，λ(T)在T<4 K时出现明显的上升。在标准BCS范围（T/Tc = 0.32）内对s波序参量的拟合将NCCO中的任何能隙限制在小于Δmin(0)/Tc = 0.57。对于PCCO，由于不存在顺磁性，使得能够进行更低温度的拟合，并得出Δmin(0)/Tc = 0.2的上限。
