Materials Viewpoint of Organic Superconductors

概要

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Since the first discovery of an organic superconductor, TMTSF_2PF_6 (TMTSF=tetramethyltetra-selenafulvalene) with the superconducting transition temperature (T_c)=0.9K under 12kbar, by the suppression of spin density wave (SDW) state, approximately 120 organic superconductors have been found. Among them, the highest T_c is 14.2K under 82kbar for β'-(BEDT-TTF)_2ICl_2 [BEDT-TTF=bis(ethylenedithio) tetrathiafulvalene]. Organic superconductors are categorized into three groups. (1) A superconducting (SC) state neighbors the SDW state, and appears by the suppression of the SDW state to afford a T_c below 1K. (2) Another SC state is competitive with a nonmagnetic insulating state induced by anion ordering, charge density wave (CDW), or charge ordering, afford a T_c below 2K. (3) Yet another SC state is next to an antiferromagnetic (AF) order to afford a T_c up to 14K under an ambient condition or a pressurized condition. In this article, organic superconductors are reviewed on the basis of a variety of molecules, and finally, recent novel organic superconductors (MDT-TS)(AuI_2)_<0.441> [MDT-TS=5H-2-(1, 3-diselenol-2-ylidene)-1, 3, 4, 6-tetrathiapentalene] obtained by suppression with an incommensurate AF state and β-(meso-DMBEDT-TTF)_2I_3 [DMBEDT-TTF=dimethylbis (ethylenedithio) tetrathiafulvalene] in competition with a checkerboard-type charge-ordered (CO) state, are introduced.
社団法人日本物理学会の論文
2006-05-15