Metal-to-insulator evolution in (NH3)(x)NaK2C60: An NMR study

Article

关键词: ELECTRONIC-PROPERTIES;    ALKALI FULLERIDES;    C-13;    TRANSITIONS;    DYNAMICS;    SHIFT;   

DOI  :  10.1103/PhysRevB.68.035102

来源: SCIE

【 摘 要 】

A singular evolution toward an insulating phase, shown by Na-23 and C-13 NMR, has been observed in the superconducting fullerides (NH3)(x)NaK2C60 for x> 1. Unlike most common cases, this insulating phase is nonmagnetic and C-13 spin lattice relaxation shows the presence of a spin gap. These two features suggest that a charge disproportion from C-60(3-) to C-60(2-) and C-60(4-) can drive the system from the metallic to the insulating state. The restoring of the Na+ cation in the center of the octahedral interstice in the insulating phase, as, indicated by Na-23 and H-2 line shape analysis, confutes the current belief that the cation off-centering is effective in quenching the superconductivity.

【 授权许可】

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