Phonon, two-magnon, and electronic Raman scattering of Fe_(1+y)Te_(1-x)Se_x

摘要

We have measured Raman-scattering spectra of single-crystalline FeTe_(0.6)Se_(0.4) (T_c ～ 14.5 K) and its parent compound Fe_(1.074)Te at various temperatures. In the parent compound Fe_(1.074)Te, A_1g and B_1g modes have been observed at 158 and 202 cm~(-1), respectively, at 5 K. These frequencies agree qualitatively with the calculated results. Two-magnon excitation has been observed around 2300 cm~(-1) for both compounds. A temperature dependence between the electronic Raman spectra below and above T_c has been observed, and 2△ and 2△/k_BT_C have been estimated as 5.0 meV and 4.0, respectively.