Anomalous 125Te Nuclear Spin Relaxation Coincident with Charge Kondo Behavior in Superconducting Pb1−xTlxTe
Year: 2018
Type: article
Abstract: We report a ^{125}Te-NMR study of single-crystalline Pb_{1-x}Tl_{x}Te for x= 0 (undoped non-superconducting "parent"), 0.35 at% (doped but on the borderline of superconductivity), and 1.0 at% (superconducting, with a critical temperature Tc ~ 1.0 K). The Knight shift in the normal state is enhanced as x increases, corresponding to an increase in the average density of states (DOS). The NMR line-width also increases significantly with increasing x, indicative of a strong spatial variation in the local DOS surrounding each Tl dopant. Remarkably, for the superconducting composition, the ^{125}Te nuclear spin relaxation rate (1/T1T) for Te ions that are close to the Tl dopants is unexpectedly enhanced in the normal state below a characteristic temperature of ~10 K. This temperature coincides with the temperature below which the normal state resistivity experiences an upturn. Such a simultaneous upturn in both the resistivity and (1/T1T) is highly anomalous, and puts Pb_{1-x}Tl_{x}Te in a distinct new class of doped semiconductors. These observations provide microscopic evidence for dynamical charge fluctuations in the absence of paramagnetism, and are consistent with expectations for charge Kondo behavior associated with the Tl dopant ions. In contrast, such anomalies were not detected in the non-superconducting samples (x=0 and 0.35 at%), suggesting a connection between dynamical valence fluctuations and the occurrence of superconductivity in Pb_{1-x}Tl_{x}Te.
Authors: Hidekazu Mukuda, Takashi Matsumura, Shota Maki, Mitsuharu Yashima, Yoshio Kitaoka, Kazumasa Miyake, Hironaru Murakami, Paula Giraldo-Gallo, Theodore H. Geball, Ian R. Fisher
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: Nuclear magnetic resonance study for high temperature superconductivity under high pressure, NMR studies of coexisting phase of antiferromagnetism and high-Tc superconductivity near Mott transition, Charge Kondo effect in valence-skipper-doped superconductor, Search for unique materials of charge Kondo effect and novel superconductivity, Theoretical Study for Anomalous Properties due to Fluctuations of Non-magnetic Degrees of Freedom, Theoretical Study on Diversity of Mechnism of Supercondcutivity in Strongly Correlated Electron Systems
OpenAlex ID: W2610866283