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arXiv 0811.4335cond-mat.supr-concond-mat.str-el
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孤子壁结构密度波背景下的超导性

Superconductivity on the density wave background with soliton-wall structure

P. D. Grigoriev

摘要:

当费米面嵌套不完善时,密度波与超导性在微观上可以共存。至少有两种可能的微观结构的DW态与准粒子态保持在费米能级上,并导致库珀不稳定性:(i)孤子壁相和(ii)小unapped费米表面口袋。这种准粒子态的色散与没有DW的情况有很大的不同,DW背景下SC的性质也有很大的不同。在这种SC状态下的上临界场$H_{c2}$随着系统接近超导性首次出现的临界压力而强烈增加。$H_{c2}$可能大大超过其无DW的典型值,并具有不寻常的向上曲率作为温度的函数。所得结果解释了层状有机超导体(TMTSF)$_{2}$ PF $_{6}$和$α$ -(BEDT TTF)$_{2}$ KHg(SCN)$_{4}$的实验观察。

英文摘要:

Superconductivity (SC) may microscopically coexist with density wave (DW) when the nesting of the Fermi surface (FS) is not perfect. There are, at least, two possible microscopic structures of a DW state with quasi-particle states remaining on the Fermi level and leading to the Cooper instability: (i) the soliton-wall phase and (ii) the small ungapped Fermi-surface pockets. The dispersion of such quasi-particle states strongly differs from that without DW, and so do the properties of SC on the DW background. The upper critical field $H_{c2}$ in such a SC state strongly increases as the system approaches the critical pressure, where superconductivity first appears. $H_{c2}$ may considerably exceed its typical value without DW and has unusual upward curvature as function of temperature. The results obtained explain the experimental observations in layered organic superconductors (TMTSF)$_{2}$PF$_{6}$ and $α$-(BEDT TTF)$_{2}$KHg(SCN)$_{4}$.

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