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  • Letter
  • Open Access

Probing mixed valence states by nuclear spin-spin relaxation time measurements

Y. Ihara1,*, M. Shimohashi1, and M. Kriener2,†

  • *Contact author: yihara@phys.sci.hokudai.ac.jp
  • †Contact author: markus.kriener@riken.jp
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Phys. Rev. Research 7, L012080 – Published 24 March, 2025

DOI: https://doi.org/10.1103/PhysRevResearch.7.L012080

Abstract

Several elements in the periodic table exhibit an interesting and often overlooked feature: They skip certain valence states, which is discussed in the field of superconductivity to be in favor of fostering higher transition temperatures Tc. However, from the experimental point of view, it is often deemed difficult to probe changes in the valence state. Here we demonstrate that the latter are accessible by the spin-spin relaxation rate 1/T2 in nuclear magnetic resonance. As target material, we chose the solid solution Ge1−xInxTe, where valence-skipping In induces superconductivity and changes its valence state as a function of x. We observe a strong enhancement in 1/T2(x) and, most importantly, find that 1/T2 and Tc exhibit a strikingly similar x dependence. These results underline the importance of valence physics for the evolution of superconductivity in Ge1−xInxTe. A model based on a Ruderman-Kittel-Kasuya-Yosida type of interaction among the In nuclei is proposed which fully accounts for the experimental results.

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Phys. Rev. Research 7, L012080– Published 24 March, 2025
  • Received 16 October 2024
  • Accepted 24 February 2025
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