Crystals 2012, 2(4), 1502-1513; doi:10.3390/cryst2041502
Article

Magnetism and Pressure-Induced Superconductivity of Checkerboard-Type Charge-Ordered Molecular Conductor β-(meso-DMBEDT-TTF)2X (X = PF6 and AsF6)

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Received: 12 September 2012; in revised form: 5 November 2012 / Accepted: 14 November 2012 / Published: 29 November 2012
(This article belongs to the Special Issue Molecular Conductors)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: The metallic state of the molecular conductor β-(meso-DMBEDT-TTF)2X (DMBEDT-TTF = 2-(5,6-dihydro-1,3-dithiolo[4,5-b][1,4]dithiin-2-ylidene)-5,6-dihydro-5,6-dimethyl-1,3-dithiolo[4,5-b][1,4]dithiin, X = PF6, AsF6) is transformed into the checkerboard-type charge-ordered state at around 75–80 K with accompanying metal-insulator (MI) transition on the anisotropic triangular lattice. With lowering temperatures, the magnetic susceptibility decreases gradually and reveals a sudden drop at the MI transition. By applying pressure, the charge-ordered state is suppressed and superconductivity appears in β-(meso-DMBEDT-TTF)2AsF6 as well as in the reported β-(meso-DMBEDT-TTF)2PF6. The charge-ordered spin-gapped state and the pressure-induced superconducting state are discussed through the paired-electron crystal (PEC) model, where the spin-bonded electron pairs stay and become mobile in the crystal, namely the valence-bond solid (VBS) and the resonant valence bonded (RVB) state in the quarter-filled band structure.
Keywords: superconductor; dimer state; checkerboard-type charge ordering; singlet state; valence bond solid; paired-electron crystal
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MDPI and ACS Style

Shikama, T.; Shimokawa, T.; Lee, S.; Isono, T.; Ueda, A.; Takahashi, K.; Nakao, A.; Kumai, R.; Nakao, H.; Kobayashi, K.; Murakami, Y.; Kimata, M.; Tajima, H.; Matsubayashi, K.; Uwatoko, Y.; Nishio, Y.; Kajita, K.; Mori, H. Magnetism and Pressure-Induced Superconductivity of Checkerboard-Type Charge-Ordered Molecular Conductor β-(meso-DMBEDT-TTF)2X (X = PF6 and AsF6). Crystals 2012, 2, 1502-1513.

AMA Style

Shikama T, Shimokawa T, Lee S, Isono T, Ueda A, Takahashi K, Nakao A, Kumai R, Nakao H, Kobayashi K, Murakami Y, Kimata M, Tajima H, Matsubayashi K, Uwatoko Y, Nishio Y, Kajita K, Mori H. Magnetism and Pressure-Induced Superconductivity of Checkerboard-Type Charge-Ordered Molecular Conductor β-(meso-DMBEDT-TTF)2X (X = PF6 and AsF6). Crystals. 2012; 2(4):1502-1513.

Chicago/Turabian Style

Shikama, Takahisa; Shimokawa, Tatsuya; Lee, Sanguchul; Isono, Takayuki; Ueda, Akira; Takahashi, Kazuyuki; Nakao, Akiko; Kumai, Reiji; Nakao, Hironori; Kobayashi, Kensuke; Murakami, Youichi; Kimata, Motoi; Tajima, Hiroyuki; Matsubayashi, Kazuyuki; Uwatoko, Yoshiya; Nishio, Yutaka; Kajita, Koji; Mori, Hatsumi. 2012. "Magnetism and Pressure-Induced Superconductivity of Checkerboard-Type Charge-Ordered Molecular Conductor β-(meso-DMBEDT-TTF)2X (X = PF6 and AsF6)." Crystals 2, no. 4: 1502-1513.

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