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Defect modulated raman response of KC<inf>8</inf> single crystals

Abstract:

In situ experiments of graphite intercalation with potassium have been performed under high vacuum (HV) conditions. A detailed Raman lineshape analysis of the G-line was applied to determine the intrinsic response of the stage one KC8 compound. Four defect-modulated graphite single crystals were analyzed. We observe five vibrational modes (~560, 1260, 1510, 1547, and 1563 cm-1). From a Breit-Wigner-Fano (BWF) lineshape analysis we elucidate the contribution of each vibrational mode observed. The intensity of the z-axis mode (CZ) around ~560 cm-1 varies depending on the defect modulated nominal KC8 crystal chosen. We prove that the intrinsic G-line of KC8 is at 1510 cm-1, and it is strongly dependent on the actual defect content in the sample, which has important implications for the electron phonon coupling (EPC) responsible of superconductivity in this system. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.