2005/01/31 by S. Lupi, M. Ortolani, Michele Ortolani +5
Chemistry · Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Charge (physics) #Charge carrier #Chemistry #Condensed matter physics #Conductivity #Doping #Electrical resistivity and conductivity #Infrared #Infrared spectroscopy #Ion #Magnetic and transport properties of perovskites and related materials #Materials science #Optical conductivity #Optics #Phonon #Physical chemistry #Physics #Physics of Superconductivity and Magnetism #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.72.024550
7 pages, 4 figures
arxiv created 2005/01/31 · openalex publication_date 2005/07/29 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The infrared conductivity \ensuremathσ(\ensuremathω) of NaxCoO2 is studied as a function of doping and temperature for 0.5\ensuremath\leqslantx\ensuremath\leqslant1. A far-infrared peak (FIP) in \ensuremathσ(\ensuremathω), which coexists with a small Drude contribution, indicates charge localization in the CoO2 layers. Long-range ordering at x=0.5 is confirmed to create a far-infrared gap, in addition to the FIP. At low T and high incommensurate x values, in correspondence with the reported formation of a spin-density wave, the FIP abruptly shifts to higher energy, indicating a deepening of the localizing potential. An analysis of the in-plane E1u phonon lifetime shows that Na+ ions lattice is ``frozen in'' at any T<295\phantom\rule0.3em0exK for commensurate x and at T\ensuremath\lesssim150\phantom\rule0.3em0exK for incommensurate x. A comparison with the behavior of the FIP suggests that the Na+ ``freezing'' induces carrier localization only for low charge density and high Na+ concentration.