Multiband superconductors: Disparity between band length scales

摘要

Multiple condensates in a superconducting material can interfere constructively or destructively and this leads to unconventional effects not inherent in single-band superconductors. Such effects can be pronounced when the spatial scales (healing lengths) of different band condensates deviate from each other. Here we show that, contrary to usual expectations, this deviation can be considerable even far beyond the regime of nearly decoupled bands, being affected by difference between the band Fermi velocities. Our study is performed within the extended Ginzburg-Landau (GL) formalism that goes to one order beyond the GL theory in the perturbation expansion of the microscopic equations over the proximity to T_c. The formalism makes it possible to obtain closed analytical results for the profiles of the band condensates and for their healing lengths and, at the same time, captures the difference between the healing lengths which does not appear in the standard GL domain.