1999 Fiscal Year Final Research Report Summary
Superconductivity and intercalation in one-dimensional conductors
| Project/Area Number |
09640426
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | Kanazawa University |
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Principal Investigator |
ISHIHARA Yutaka Faculty of Science, Physics, Kanazawa University Professor, 理学部, 教授 (10019474)
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| Co-Investigator(Kenkyū-buntansha) |
KANEKO Hiroshi Graduate school of natural science and technology, Kanazawa University Assistant, 自然科学研究所, 助手 (40272942)
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| Project Period (FY) |
1997 – 1999
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| Keywords | intercalation / superconductivity / one-dimensional conductor / resistivity / thermoelectric power / charge-density wave / 遷移金属化合物 |
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| Research Abstract |
The electrical resistivity and the thermoelectric power of NbィイD23ィエD2TeィイD24ィエD2 inserted with Hg and In have been measured in the temperature range from 1.4 to 300 K : HgィイD2xィエD2NbィイD23ィエD2TeィイD24ィエD2 and InィイD2xィエD2NbィイD23ィエD2TeィイD24ィエD2. The magnitude of the resistivity and the residual-resistivity ratio is not greatly affected by addition of Hg or In. The resistivity of NbィイD23ィエD2TeィイD24ィエD2 shows two anomalies at 40 K and 110 K. These resistivity anomalies disappear by addition of Hg. On the contrary, both resistivity anomalies are enhanced when adding a small amount of In and a new resistivity anomaly appears at 160 K for x > 0.3. The anomalies in the thermoelectric power curve also appear at the range in temperature where the resistivity anomalies appear. The sign of the thermoelectric power changes from negative to positive with addition of In. The superconducting transition temperature is enhanced from 1.9 to 5.4 K by addition of Hg. These results are discussed on the basis of the multiband model with electronlike and holelike carriers.
The pressure effect on the superconductivity and on the CDW formation in NbィイD23ィエD2XィイD24ィエD2 with X=S, Se, and Te has been studied by a resistivity measurement. In both NbィイD23ィエD2SィイD24ィエD2 and NbィイD23ィエD2SeィイD24ィエD2, the superconducting-transition temperature TィイD2cィエD2 decreases with increasing pressure. Pressure-induced-lattice stiffening mainly causes the decrease of TィイD2cィエD2 in these compounds. The TィイD2cィエD2 of NbィイD23ィエD2TeィイD24ィエD2 increases with pressure. The pressure enhancement of TィイD2cィエD2 is mainly due to the increase of N(0) by the recovery of the density of states N(0) associated with the depression of the CDW's. The pressure effect on both CDW-transition temperatures is discussed in terms of both lattice stiffening and collapse of the nesting of the Fermi surfaces.
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