HMTSF-TCNQ is a quasi-one-dimensional organic conductor which undergoes CDW(charge density wave) transition at 30 K at ambient pressure, where HMTSF-TCNQ is hexamethylenetetraselena fulvalene-tetracyano quino dimethane. This CDW is suppressed by the pressure of 1 GPa. At this pressure, we found field-induced successive hysteretic transitions in magnetoresistance. This reminds us of the successive field-induced SDW (spin density wave) phases in TMTSF2X salts. However, the field range of interest is 2-3 times higher than that of TMTSF2X salts. Therefore, we need really high field to examine these properties. It is very likely that the field induced phases are of field induced CDW (FICDW), where quantum Hall effect and many interesting phenomena are expected like in the case of FISDW. Together with the magnetoresistance study up to the field of 31 Tesla and at temperatures down to 0.4 K in various magnetic field angles respective to the crystal axes, we examined the angular dependence of magnetoresistance oscillations(AMRO). It turned out that AMRO demonstrates clearly the occurrence of field-induced phase rather than the magneto-resistance by field sweep. Since the Hall resistance, R xy in the field-induced phases showed stepwise plateau structure against the field sweep, and its strength was in the order of magnitude of h/e 2 per molecular sheet, the Hall effect is very suggestive of quantum Hall effect.
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Acknowledgements We appreciate Dr. H. Fujiwara (Osaka Prefecture University) for checking the crystals by X-ray diffraction. This work was partially supported by the government of Japan by the Grant-in-Aid for priority area 23110722. W.K. is supported by the government of Korea through NRF Grants (2012-0000539 and 0030902). Work done in part at the NHMFL, supported by USA government by NSF-DMR-0654118, the State of Florida, and the DOE, and by NSF-DMR-1005293 (J.S.B.).
- High pressure
- Organic conductor
- Quantum Hall effect
- Quasi one dimension