Collective excitations of two-phase Bi2223 and Bi2212 superconducting condensates in Bi-based high-temperature superconductors

Typically, bismuth-based high-temperature superconductors (HTSCs) consist of two superconducting phases: Bi2Sr2Ca2Cu3Ox (Bi2223) and Bi2Sr2CaCu2Ox (Bi2212). To specify the dynamical coupling of the superconducting condensates of these phases, a series of Bi-based HTSC samples with different fractions of Bi2223 and Bi2212 phases have been prepared and investigated. Using point-contact Andreev spectroscopy, collective excitations in Bi2Sr2Ca2Cu3Ox + Bi2Sr2CaCu2Ox superconductors related to the superconducting binding of two-phase states of Bi-based HTSC have been revealed. The experimentally detected Leggett-like excitations reveal the Josephson coupling of multicomponent superconducting states in Bi-HTSC.