Photoconductivity and optical conductivity in lightly doped Nd2CuO4−δ

✍ Scribed by G. Yu; C.H. Lee; A.J. Heeger; S.-W. Cheong

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 637 KB
• Volume: 203
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(92)90051-d

✦ Synopsis

The photoconductivity, Q(W), and the optical conductivity, a(w), of lightly-doped single crystals of NdZCu04_-d are compared over the photon energy range 0.6 < fiw < 3 eV. We find that crphph( w ) and u( w ) exhibit a common edge at the charge transfer energy gap, 1.2 eV, with no indication of a significant exciton binding energy. At higher photon energies, Q(W) follows u(w). At energies below the charge transfer transition, a broad spectral feature is observed in u(w), centered at 0.6-0.7 eV. This feature is suppressed in Use, which shows a weak and relatively narrow peak at 0.7 eV at relevant temperatures.

The discrepancies between Q(W) and u(w) in the infrared spectral region provide evidence that the states in the CT band tails and the broad, doping-induced gap states in the CuO, layers are localized.