Pressure dependence of coherence-incoherence crossover behavior in KFe2As2 observed by resistivity and As-75-NMR/NQR

Article

关键词: IRON-BASED SUPERCONDUCTORS;    TEMPERATURE SUPERCONDUCTIVITY;    MAGNETIC-RESONANCE;    T-C;    ORDER;    METALS;   

DOI  :  10.1103/PhysRevB.97.064509

来源: SCIE

【 摘 要 】

We present the results of As-75 nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), and resistivity measurements in KFe2As2 under pressure (p). The temperature dependence of the NMR shift, nuclear spin-lattice relaxation time (T-1), and resistivity show a crossover between a high-temperature incoherent, local-moment behavior and a low-temperature coherent behavior at a crossover temperature (T*). T* is found to increase monotonically with pressure, consistent with increasing hybridization between localized 3d orbitalderived bands with the itinerant electron bands. No anomaly in T* is seen at the critical pressure p(c) = 1.8 GPa where a change of slope of the superconducting (SC) transition temperature T-c(p) has been observed. In contrast, T-c(p) seems to correlate with antiferromagnetic spin fluctuations in the normal state as measured by the NQR 1/T1 data, although such a correlation cannot be seen in the replacement effects of A in the AFe(2)As(2) (A = K, Rb, Cs) family. In the superconducting state, two T-1 components are observed at low temperatures, suggesting the existence of two distinct local electronic environments. The temperature dependence of the short T-1s indicates a nearly gapless state below T-c. On the other hand, the temperature dependence of the long component 1/T-1L implies a large reduction in the density of states at the Fermi level due to the SC gap formation. These results suggest a real-space modulation of the local SC gap structure in KFe2As2 under pressure.

【 授权许可】

Free