三重态双极化子系统的超导与铁磁共存

采用对称破缺的Hartree平均场近似,讨论了三重态双极化子系统的超导和铁磁共存问题。我们发现,系统的基态是铁磁超导混合态,这与BCS超导的情形不同。在双极化子的低密度区域,只有从正常态到混合态的转变;而在高密度区域,随着温度的降低,系统可能将首先转变到铁磁态,然后转变到铁磁超导混合态。当系统已经具有超导电性时,不可能发生到铁磁态的相变。 关键词：

COEXISTENCE OF SUPERCONDUCTIVITY AND FERROMAGNETISM IN THE TRIPLET BIPOLARONIC SYSTEM

The problem of coexistence of superconductivity and ferromagnetism in the triplet bipolaro-nic system has been studied by using the symmetry-broken Hartree approximation. It is found that the ground stare of the system is the mixed state of both orders, which is different from the case of usual BCS systems. It is seen from the phase diagram obtained that in the high bipolaro-nic concentration region the system may exhibit a transition from the ferromagnetic to the mixed state on cooling, while in the low concentration region only the transition from the normal to the mixed state is possible.