Infrared study of La1.92Sr0.08CuO4 and La1.85Sr0.15CuO4 single crystals

Abstract Infrared reflectivity temperature measurements have been measured on two La 2− x Sr x CuO 4 single crystals with x  = 0.08 (underdoped) and x  = 0.15 (optimally doped), in-plane and out-of-plane. The obtained optical conductivity results suggest the existence of the pseudo-gap phase only for the underdoped sample.