Suppression of fluctuations in a two-band superconductor with a quasi-one-dimensional band

Physical Review B: Condensed Matter and Materials Physics. 2022. Vol. 105. No. 21. Article 214527.

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

Chainlike structured superconductive materials (such as A2Cr3As3, 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 Tc0 and fluctuation-shifted Tc 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 Tc is close to Tc0 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.

Keywords: Renormalization, ренормгруппа, high temperature superconductors, высокотемпературные сверхпроводники, многозонные сверхпроводники, обычная и расширенная теории Гинзбурга-Ландау, ordinary and extended Ginzburg-Landau theory, multiband superconductivity

Publication based on the results of: Investigations of quantum effects in low-dimensional materials (2022)