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

Date
2018-02-01
Authors
Wiecki, Paul
Taufour, V.
Chung, D.
Canfield, Paul
Kanatzidis, M.
Bud’ko, Sergey
Canfield, Paul
Furukawa, Yuji
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Altmetrics
Authors
Research Projects
Organizational Units
Ames Laboratory
Organizational Unit
Physics and Astronomy
Organizational Unit
Journal Issue
Series
Department
Ames LaboratoryPhysics and Astronomy
Abstract

We present the results of 75 As nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), and resistivity measurements in KFe 2 As 2 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 3 d orbital-derived 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 / T 1 data, although such a correlation cannot be seen in the replacement effects of A in the A Fe 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 1 s indicates a nearly gapless state below T c . On the other hand, the temperature dependence of the long component 1 / T 1 L 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 KFe 2 As 2 under pressure.

Comments
Description
Keywords
Citation
DOI
Collections