Conductivity in Cuprates Arises from Two Different Sources: One-Electron Exchange and Disproportionation
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- 作者：Sven Larsson
- 关键词：Cuprates ; Resistivity ; Superconductivity (SC) ; Doping level ; Hubbard ; U ; Pseudogap ; Metal ; metal charge transfer (CT) ; Vibronic states ; Mobility
- 刊名：Journal of Superconductivity and Novel Magnetism
- 出版年：2017
- 出版时间：February 2017
- 年：2017
- 卷：30
- 期：2
- 页码：275-285
- 全文大小：845KB
- 刊物类别：Physics and Astronomy
- 刊物主题：Strongly Correlated Systems, Superconductivity; Magnetism, Magnetic Materials; Condensed Matter Physics; Characterization and Evaluation of Materials;
- 出版者：Springer US
- ISSN：1557-1947
- 卷排序：30
文摘
Simulation of the resistivity in the normal state of doped La2−xSrxCuO4 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 (ρ) decreases from almost insulation at T = 0 to a minimum at about T = 100 K. ρ then increases more than linearly with T (∼T3/2) in the region 100 < T < 500 K. A photo-induced metal-metal (MM) charge transfer transition at 2 eV 2Cu(II) + h ν→ 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−xSrxCuO4 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.