Raman evidence for the superconducting gap and spin–phonon coupling in the superconductor Ca(Fe 0.95 Co 0.05 ) 2 As 2 (original) (raw)

Inelastic light scattering studies on single crystal of electron-doped Ca(Fe 0.95 Co 0.05 ) 2 As 2 superconductor, covering the tetragonal to orthorhombic structural transition as well as magnetic transition at T SM ~ 140 K and superconducting transition temperature T c ~ 23 K, reveal evidence for superconductivity-induced phonon renormalization; in particular the phonon mode near 260 cm -1 shows hardening below T c , signaling its coupling with the superconducting gap. All the three Raman active phonon modes show anomalous temperature dependence between room temperature and T c i.e phonon frequency decreases with lowering temperature. Further, frequency of one of the modes shows a sudden change in temperature dependence at T SM . Using first-principles density functional theory-based calculations, we show that the low temperature phase (T c < T < T SM ) exhibits short-ranged stripe anti-ferromagnetic ordering, and estimate the spinphonon couplings that are responsible for these phonon anomalies.