A study of the magnetoresistance of the charge-transfer salt at hydrostatic pressures of up to 20 kbar: evidence for a charge-density-wave ground state and the observation of pressure-induced superconductivity
| Autor: | J. M. Caulfield, W. Lubczynski, C.J. Kepert, M. Kurmoo, L. Du Croo De Jongh, S. J. Blundell, S V Demishev, William Hayes, Peter Day, John Singleton |
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| Rok vydání: | 1996 |
| Předmět: | |
| Zdroj: | Journal of Physics: Condensed Matter. 8:6005-6017 |
| ISSN: | 1361-648X 0953-8984 |
| DOI: | 10.1088/0953-8984/8/33/009 |
| Popis: | The magnetoresistance of single crystals of the quasi-two-dimensional (Q2D) organic conductor has been studied at temperatures between 700 mK and 300 K in magnetic fields of up to 15 T and hydrostatic pressures of up to 20 kbar. Measurements of the resistivity using a direct-current van der Pauw technique at ambient pressure show that the material undergoes a metal-to-insulator transition at ; below this temperature the resistivity increases by more than five orders of magnitude as the samples are cooled to 4.2 K. If the current exceeds a critical value, the sample resistivity undergoes irreversible changes, and exhibits non-ohmic behaviour over a wide temperature range. Below 30 K, either an abrupt increase of the resistivity by two orders of magnitude or bistable behaviour is observed, depending on the size and/or direction of the measurement current and the sample history. These experimental data strongly suggest that the metal - insulator transition and complex resistivity behaviour are due to the formation of a charge-density wave (CDW) with a well-developed domain structure. The magnetotransport data recorded under hydrostatic pressure indicate that pressure has the effect of gradually reducing the CDW ordering temperature. At higher pressures, there is a pressure-induced transition from the CDW state to a metallic, superconducting state which occurs in two distinct stages. Firstly, a relatively small number of Q2D carriers are induced, evidence for which is seen in the form of the magnetoresistance and the presence of Shubnikov - de Haas oscillations; in spite of the low carrier density, the material then superconducts below a temperature of . Subsequently, at higher pressures, the CDW state collapses, resulting in Q1D behaviour of the magnetoresistance, and eventual suppression of the superconductivity. |
| Databáze: | OpenAIRE |
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