We report X-band electron paramagnetic resonance (EPR) and T 125 e and S 77 e NMR measurements on single-crystalline superconducting FeSe0.42 Te0.58 [Tc =11.5 (1) K]. The data provide indications for the coexistence of intrinsic localized and itinerant electronic states. In the normal state, localized moments couple to itinerant electrons in the Fe(Se,Te) layers and affect the local spin susceptibility and spin fluctuations. Below Tc, spin fluctuations become rapidly suppressed and an unconventional superconducting state emerges in which 1/ T1 is reduced at a much faster rate than expected for conventional s - or s± -wave symmetry. We suggest that the localized states arise from the strong electronic correlations within one of the Fe-derived bands. The multiband electronic structure together with the electronic correlations thus determine the normal and superconducting states of the FeSe1-x Tex family, which appears much closer to other high- Tc superconductors than previously anticipated.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2010 Oct 25|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics