Phase Diagrams and the Physics of the Pseudogap in Superconductors with Attractive Interaction

Kagan, M. Yu.

doi:10.1007/978-94-007-6961-8_8

Cited by 1 publication

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“…[24]. We mention that the formation of negative-U centers by defects or interstitials in the range close to the bottom of the conduction band is of high interest in doped perovskites where defects or interstitials [25,26] have been proposed to create negative-U centers playing a key role in high temperature superconductivity [27][28][29]. In the present case, as will be explained below in detail, the negative-U behaviour is related to a strong coupling between the vacancy charge and the vacancy geometry.…”

Section: Resultsmentioning

confidence: 99%

Oxygen and potassium vacancies in KTP calculated from first principles

Bocchini

Neufeld²,

Gerstmann³

et al. 2019

J. Phys.: Condens. Matter

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The atomic geometry and energetics of oxygen and potassium vacancies in potassium titanyl phosphate (KTP) as well as their electronic and optical properties are studied within density-functional theory in dependence of their charge state. Oxygen vacancies formed between Ti and P are characterized by a negative-U behavior. Their neutral charge state is favored for Fermi levels near the conduction band and gives rise to a defect level in the band gap, which leads to an additional optical absorption peak. In contrast, the two-fold positive charge state, stable for low and intermediate values of the Fermi level, modifies the KTP optical response only slightly. Oxygen vacancies formed between two Ti atoms are two-fold positively charged, while potassium vacancies are negatively charged irrespective of the Fermi level position. In both these cases, the KTP optical response is essentially not affected.

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