Transport properties of Andreev polarons in a superconductor-semiconductor-superconductor junction with superlattice structure

Transport properties of a superconductor-semiconductor-superconductor (Su-Sm-Su) junction with superlattice structure are investigated. Differential resistance as a function of voltage shows oscillatory behavior under the irradiation of radio-frequency (rf) waves with the specific frequency of 1.77 GHz regardless of the superconducting materials and the junction geometries. Experimental data are quantitatively explained in terms of the coupling of superconducting quasiparticles with long-wavelength acoustic phonons indirectly excited by the rf waves. We propose that the strong coupling causes the formation of novel composite particles, Andreev polarons.