The non-Drude type of optical conductivity in cuprates

There is a long-standing issue that the optical conductivity in normal-state of cuprate superconductors deviates the conventional Drude type marked by ω−2 dependence, exhibiting two main components from underdoping to overdoping, a narrow band peaked around zero energy and a broadband centered in the mid-infrared region called mid-infrared band. Within the renormalized t-J model and self-consistent mean field theory, we discuss the doping and energy dependence of optical conductivity in cuprate superconductors. Our results show that the appearance of the pseudogap in normal state is responsible for anomalous optical conductivity, giving rise to the mid-infrared band. In particular, in analogy to the doping dependence of pseudogap, optical conductivity is also strongly doping dependent. By increasing the doping concentration, the spectral weight of the optical conductivity suppressed strongly in underdoped region increases quickly, and the peak position of the mid-infrared band moves towards to the lower e...