{sup 125}Te-NMR Study in Novel Superconductor Pb{sub 1−x}Tl{sub x}Te with Valence Skipping Dopants
- Osaka University, Graduate School of Engineering Science (Japan)
- Osaka University, Center for Advanced High Magnetic Field Science (Japan)
- Osaka University, Institute of Laser Engineering (Japan)
- Stanford University, Department of Applied Physics (United States)
Pb{sub 1−x}Tl{sub x}Te is an anomalous low carrier density superconductor for which the origin of the superconductivity is not understood. Thallium is the only dopant to cause superconductivity in PbTe, suggesting that these specific impurities have a unique effect on the electronic states. Systematic {sup 125}Te-NMR studies on single-crystallines Pb{sub 1−x}Tl{sub x}Te (x = 0, 0.35, 1.0 at%) reveal that the Tl dopants induce spatially inhomogeneous electronic states around the Tl dopants. In the superconducting sample at x = 1.0 at%, {sup 125}Te nuclear spin relaxation rate (1/T{sub 1}T) in the vicinity of the Tl dopants is unexpectedly enhanced below ∼10 K. This coincides with the temperature below which the resistivity exhibits an upturn. By contrast, such anomalies were not detected in the non-superconducting sample at x = 0.35 at%. These observations can be consistently explained by charge Kondo effect, in which two nearly degenerate valence states of the Tl dopant form a resonating valence state upon cooling below 10 K. Based on these observations, we suggest that the coherent hopping of 6s-electron pair may provide the pairing interaction (i.e., a negative-U scenario), leading to the anomalously high T{sub c} found for Pb{sub 1−x}Tl{sub x}Te.
- OSTI ID:
- 22921224
- Journal Information:
- Journal of Superconductivity and Novel Magnetism, Vol. 32, Issue 6; Other Information: Copyright (c) 2019 Springer Science+Business Media, LLC, part of Springer Nature; Country of input: International Atomic Energy Agency (IAEA); ISSN 1557-1939
- Country of Publication:
- United States
- Language:
- English
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