The Existence of the 60 K Plateau in the YBa2Cu3O6+y Phase Diagram: the Role of Oxygen Ordering and Charge Imbalance |
| T.A. Zaleski and T.K. Kopeć
Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław, Poland |
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| We propose a semi-microscopic model of YBa2Cu3O6+y to investigate the origin of the 60 K plateau in its phase diagram. Our model is a "phase only" approach to the high-temperature superconducting system in terms of collective variables. It is able to capture characteristic energy scales present in YBa2Cu3O6+y by using adjustable parameters representing phase stiffnesses and allows for strong anisotropy within basal planes to simulate oxygen ordering. We solve the model calculated Tc for chosen system parameters investigating the influence of oxygen ordering and doping imbalance on the shape of YBa2Cu3O6+y phase diagram. Our results suggest that the oxygen ordering alone does not seem to be responsible for the existence of the 60 K plateau. However, relying on experimental data unveiling that oxygen doping of YBa2Cu3O6+y may introduce a significant charge imbalance between CuO2 planes and other sites, we show that simultaneously the former are underdoped, while the latter - strongly overdoped almost in the whole region of oxygen doping in which YBa2Cu3O6+y is superconducting. This provides two natural counter acting factors, which possibly lead to rise the 60 K plateau with increasing oxygen doping. |
| DOI: 10.12693/APhysPolA.111.705 PACS numbers: 74.20-z, 74.72.Bk, 74.62.-c |