期刊
PHYSICAL REVIEW B
卷 83, 期 17, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.83.174510
关键词
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资金
- NSFC [10974254, 11034012, 11074304]
- National Basic Research Program of China [2010CB923000, 2011CBA00100]
- Program for New Century Excellent Talents in University
- Fundamental Research Funds for the Central Universities
We report both Se-77 and Rb-87 nuclear magnetic resonance (NMR) studies on Tl0.47Rb0.34Fe1.63Se2 single-crystalline superconductors (T-c approximate to 32 K). Singlet superconductivity is suggested by a sharp drop of the Knight shift K(T) below T-c, after subtracting the superconducting diamagnetic effect. However, the Hebel-Slichter coherence peak below T-c is not observed in the spin-lattice relaxation rate 1/T-1, even with a low in-plane NMR field of 2.6 T. Just above T-c, no evidence of low-energy spin fluctuation is found in the spin-lattice relaxation rate on both the Se-77 and the Rb-87 sites. Upon warming, however, the Knight shifts and the spin-lattice relaxation rates of both nuclei increase substantially with temperature. In particular, the Knight shift is nearly isotropic and follow a function fit of K = a + bT(2) from T-c up to 300 K. Our observations should put a strong constraint to the theory of magnetism and superconductivity in the recently discovered iron selenide superconductors.
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