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.

Luminescence of a cooper pair.

This Letter theoretically discusses the photon emission spectra of a superconducting p-n junction. On the basis of the second order perturbation theory for electron-photon interaction, we show that the recombination of a Cooper pair with two p-type carriers causes enhancement of the luminescence intensity. The calculated results of photon emission spectra explain characteristic features of observed signal in an recent experiment. Our results indicate high functionalities of superconducting light-emitting devices.

Generation of a broadband spectral comb with multiwave mixing by exchange of an impulsively stimulated phonon.

A broadband spectral comb is generated around the third harmonics of incident light with the nondegenerate, impulsively stimulated Raman scattering technique using ultrashort light pulses. The comb has a spectral width of more than 4000 cm(-1), and its envelope becomes smooth as the light powers are increased. It consists of discrete lines, the spacing of which is equal to the frequency of the Raman-active phonon mode, even though the frequency of the phonon mode is far smaller than the frequency difference between the two incident light pulses. The multiline structure is generated with multiwave mixing by exchange of the impulsively stimulated phonon among the signals.

Anomalously broad Raman scattering spectrum due to two-magnon excitation in hexagonal YMnO3.

A strong and broad Raman scattering (RS) spectrum is observed from two-magnon processes in YMnO3. The spectrum is analyzed by taking account (i) the magnon-exciton interaction and (ii) the magnon-phonon coupling in the intermediate state. Anomalous broadening of the RS is attributed to the large superexchange interaction between manganite ions and subsequent modification of magnons under the presence of the exciton and phonons in the intermediate state.