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arXiv 2202.07640cond-mat.supr-con
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具有准一维带的双带超导体中涨落的抑制

Suppression of fluctuations in a two-band superconductor with a quasi-1D band

A. A. Shanenko, T. T. Saraiva, A. Vagov, A. S. Vasenko, A. Perali

摘要:

链状超导材料(如A_2Cr_3As_3,其中A = K,Rb,Cs)具有单粒子态的多带电子结构,其中准一维(Q1D)能带和常规的高维能带共存,参与了凝聚态超导凝聚体的形成。在单带超导体中,当化学势接近Q1D带的边缘时,相应的平均场临界温度显著升高,但超导性被涨落猝灭。然而,最近的研究表明,当一个Q1D带耦合到一个更高的维度,通过带间的库珀对转移,可以抑制的热涨落,从而得到的临界温度可以接近其平均场值。本文计算了Q1D带与高维带共存的双带超导体的平均场Tc 0和涨落漂移Tc临界温度,并研究了热涨落对系统参数的敏感性.我们发现,在很大范围的微观参数下,T_c接近T_c0,甚至更高维能带的维度也不起重要作用。因此,通过带间的对交换耦合来抑制波动的屏蔽机制确实与大类Q1D多带超导材料相关,鼓励进一步的实验,旨在在这种多带超导体中达到更大的临界温度。

英文摘要:

Chain-like structured superconductive materials (such as A_2Cr_3As_3, with A = K, Rb, Cs) exhibit the multiband electronic structure of single-particle states, where coexisting quasi-one-dimensional (Q1D) and conventional higher-dimensional energy bands take part in the creation of the aggregate superconducting condensate. When the chemical potential approaches the edge of a Q1D band in a single-band superconductor, the corresponding mean-field critical temperature increases significantly but the superconductivity is quenched by fluctuations. However, recent investigation has revealed that when a Q1D band is coupled to a higher dimensional one by the interband Cooper-pair transfer, the thermal superconductive fluctuations can be suppressed so that the resulting critical temperature can be close to its mean-field value. In the present work, we calculate the mean-field T_c0 and fluctuation-shifted T_c critical temperatures for a two-band superconductor where a Q1D band coexists with a higher-dimensional band, and investigate how the thermal fluctuations are sensitive to the system parameters. We find that T_c is close to T_c0 in a wide range of microscopic parameters, and even the dimensionality of the higher-dimensional band does not play an essential role. Thus, the screening mechanism for suppressing fluctuations via the pair-exchange coupling between the bands is indeed relevant for a large class of Q1D multiband superconducting materials, encouraging further experiments aimed at reaching larger critical temperatures in such multiband superconductors.

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