| Budget Amount *help |
¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2005: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2004: ¥600,000 (Direct Cost: ¥600,000)
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| Research Abstract |
We have reproduced a phase diagram in temperature and magnetic field plane in the organic superconductor κ-(BETS)2FeBr4 theoretically. In this compound, it was known that not only field-induced superconductivity (FISC) in high magnetic field, but also superconductivity occurs in low magnetic fields, and at low fields antiferromagnetic long-range order coexists with superconductivity. We extended the Jaccarino-Peter mechanism of the FISC to antiferromagnetic superconductors. Based on values of model parameters that are determined from the critical fields of the FISC, we have reproduced upper critical fields of low temperature superconductivity quantitatively. This results suggests that the extended Jaccarino-Peter mechanism takes place in a real material. According to this mechanism, we could predict that upper critical field may be enhanced up to a value which is much larger than the Pauli paramagnetic limit in a certain kind of antiferromagnetic superconductors. In addition, we have examined possibility of the FFLO state in this compound. It has been found that the FFLO hardly occurs in the FISC in contrast to the λ-(BETS)2FeCl4 compound, while it may occur in low-field superconductivity.
We have examined the anisotropy and the pairing mechanism of superconductivity in the heavy fermion superconductor. UPd2Al3. We have pointed out that in this compound intralayer pairing is prohibited by the coexisting antiferromagnetic long-range order. Furthermore, we have pointed out that the antiferromagnetic exchange interactions that stabilize the antiferromagnetic long-range order like one observed in this compound play a role of interlayer singlet pairing interactions, and such a singlet order parameter is not influenced the coexisting antiferromagnetic order at all. These results are consistent with recent thermalconductivity and nuclear magnetic resonance data.
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