Interpretation of anomalous normal state optical conductivity of K 3 C 60 fullerides

• DOI: 10.1007/s12034-013-0441-8
• Publication Date: 2013-04-01T03:13:31Z
• Authors: K K CHOUDHARY
• Keywords: 0103 physical sciences; 01 natural sciences

The observed frequency dependent optical response of alkali–metal-doped fulleride superconductors (T c ≈ 19 K) has been theoretically analysed. The calculations of the optical conductivity, σ(ω), have been made within the two-component schemes: one is the coherent Drude carriers (electrons) responsible for superconductivity and the other is incoherent motion of carriers from one atom to other atom of C60 molecule to a pairing between Drude carriers. The approach accounts for the anomalies reported (frequency dependence of optical conductivity) in the optical measurements for the normal state. The model has only one free parameter, the relaxation rate. The frequency dependent relaxation rates are expressed in terms of memory functions. The coherent Drude carriers form a sharp peak at zero frequency and a long tail at higher frequencies, i.e. in the infrared region. However, the hopping of carriers from one atom to the other (incoherent motion of doped electrons) yields a peak value in the optical conductivity centred at mid-infrared region. It is found that both the Drude and hopping carriers will contribute to the optical process of conduction in the K3C60 and shows similar results on optical conductivity in the mid-infrared as well as infrared frequency regions as those revealed from experiments.