1994 Fiscal Year Final Research Report Summary
DYNAMICS AND PHASE TRANSITIONS OF SPIN-DENSITY WAVES
| Project/Area Number |
04402007
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
SAMBONGI Takashi Hokkaido University, Faculty of Science, Professor, 理学部, 教授 (60000791)
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| Co-Investigator(Kenkyū-buntansha) |
HIRAO Ken-iti Hokkaido University, Graduate School of Enviromental Science, Professor, 大学院・地球環境科学研究科, 教授 (60001757)
ONODERA Akira Hokkaido University, Faculty of Science, As Professor, 理学部, 助教授 (40142682)
NOMURA Kazushige Hokkaido University, Faculty of Science, Professor, 理学部, 教授 (80128579)
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| Project Period (FY) |
1992 – 1994
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| Keywords | Bechgaard salt / Spin-density wave / Sliding / Semi-metallic SDW / Threshold field / Current oscillation / Transient oscillation / Pinning |
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| Research Abstract |
Electrical conductivity of (TMTSF)_2AsF_6, a typical organic charge transfer salt was studied. Pressure, temperature and electric field-dependences of the conductivity were obtained. The metal-semimetal transition temperature and the thermal activation energy in the spin-density wave phase were determined as functions of pressure. It was concluded that the metal-semimetal transition is not associated with the normal to the spin-density wave transition ; a semi-metallic spin-density wave phase exists above the transition temperature especially near the critical presure At moderate pressure, the threshold electric field for the non-linear conductivity due to the sliding of the spin-density wave was obtained as the function of temperature. The results were compared with the theory by Maki and others. It is likely that the spin-density wave in this system in the temperature range above 3K is pinned by the commensurability with the lattice, not by impurities. This is the first finding of th
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e spin-density wave with the commensurate wave vector among the Bechgaard salts. It was that the temperature dependences of both the threshold field and of the non-linear conductivity change at 3K under low pressure. From the results, it was concluded that there is a phase transition in the spin-density wave ordered phase, though it has not been possible to identify the trasiton mechanism. The measurements were extended down to 0.6K using He3. From results obtained at lower temperature, it was found that the sliding mechanism unique in the entire temperature range can be understood in terms of a semi-classical picture. It was found that the threshold field increases with decreasing cross-sectional area of samples, and that the temperature dependence of the threshold field of thin samples is different from that of thick crystals. It was pointed out that furface of crystals is effective in pinning and sliding of density waves. Transient oscillation was observed in response voltage wave form under pulse current. Its frequency is proportional to the non-linear component of current and is equal to the frequency of narrow band noise under DC current. Its proportionality constant, independent of temperature, is proportional to the sliding velocity. Less
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Research Products
(15 results)
