Leggett's mode in Mg1-xAlxB2

A detailed investigation of multiband superconductivity and Leggett's mode in the Mg1-xAlxB2 (0 <= x <= 0.45) system was carried out using tunneling and Andreev spectroscopy. Temperature dependences of superconducting gaps Delta(sigma) and Delta(pi) and their variation upon the degree of disorder and the Al concentration were studied. The dependence of the Leggett's mode energy epsilon(0) upon the values of the gaps Delta(sigma) and Delta(pi) has been derived.