Electron–phonon coupling in Nb-dopedSrTiO3 single crystal

Abstract

Near normal incident infrared reflectivity spectra of (001)SrTi1−xNbxO3 single crystal have been measured at different temperatures in the frequency region between 100 and6000 cm−1. The optical parameters of phonons and plasmons are obtained on the basis of thedouble-damping extended Drude model. The lowest frequency phonon mode at175 cm−1 softens with decreasing temperature, and the plasmon frequency triples whenthe temperature decreases from 300 to 10 K. Extra absorption near the highestfrequency longitudinal phonon mode shows that the effect of the polaronsshould be taken into account in addition to the plasmon–phonon coupling. Thesplitting of the last high reflectivity band, the temperature dependence of the615 cm−1 structure and the appearance of a new weak peak-like defect mode provide evidence for theexistence of small polarons.