Stretched exponential spin relaxation in organic superconductors

Joseph Gezo, Tak Kei Lui, Brian Wolin, Charles P. Slichter, Russell Giannetta, John A. Schlueter

Research output: Contribution to journalArticle

Abstract

Proton NMR measurements on the organic superconductor κ-(ET) 2Cu[N(CN)2]Br [where ET represents bis(ethylenedithio) tetrathiafulvalene] TC=11.6K exhibit stretched exponential spin-lattice relaxation below T≈25K, suggestive of an inhomogeneous magnetic phase that develops in the normal state and coexists with superconductivity. The onset of this phase coincides approximately with a large normal-state Nernst signal reported previously. By contrast, the closely related superconductor κ-(ET)2Cu(NCS)2 TC=10.5K shows single exponential spin-lattice relaxation and a conventional Nernst effect. The temperature range of TC < T < 30 K encompasses several phenomena in the κ-(ET)2X conductors, including changes in conduction-electron-spin resonance, electronic phase separation, and the onset of antiferromagnetic order. Analogous behavior in La2-xSr xCuO4 suggests that a spin glass or density wave may develop in κ-(ET)2Cu[N(CN)2]Br.

Original languageEnglish (US)
Article number140504
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume88
Issue number14
DOIs
StatePublished - Oct 14 2013

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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