Conductivity in Cuprates Arises from Two Different Sources: One-Electron Exchange and Disproportionation
Artikel i vetenskaplig tidskrift, 2017

Simulation of the resistivity in the normal state of doped La2-x Sr (x) CuO4 has been performed using a hopping model based on Marcus theory. The results are in substantial agreement with experimental results. At oxidative doping, Cu(III) sites are formed and electron mobility possible due to hopping: Cu(III)Cu(II) -> Cu(II)Cu(III) (one-electron exchange). In the underdoped, non-metallic region, the resistivity (rho) decreases from almost insulation at T = 0 to a minimum at about T = 100 K. rho then increases more than linearly with T (similar to T (3/2)) in the region 100 < T < 500 K. A photo-induced metal-metal (MM) charge transfer transition at 2 eV 2Cu(II) + h nu -> Cu(I) + Cu(III) is responsible for the strong absorption in the visible spectrum of La2CuO4. The down-shift of spectral density with doping (x) in La2-x Sr (x) CuO4 depends on the appearance of Cu(III) sites which makes optical as well as thermal one-electron exchange transitions possible with lower energy. Disproportionation occurs spontaneously for x > 0.06, opening up for electron pair formation. Configuration interaction between two-electron states of low chemical potential, but strong vibrational coupling, gives rise to the superconductor and pseudogaps. Data from photo-induced conductivity and absorption spectra are used in the simulation, which gives results in good agreement with experiments. Possible explanations for Raman and MIR absorption suggest themselves.


Superconductivity (SC)

Doping level

Metal-metal charge transfer (CT)





Vibronic states


Sven Larsson

Kemi och kemiteknik, Kemi och biokemi, Fysikalisk kemi

Journal of Superconductivity and Novel Magnetism

1557-1939 (ISSN) 1557-1947 (eISSN)

Vol. 30 275-285


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