T_c-variations of R_1_-_yCa_yBa_2Cu_3O_x under high pressure: Influence of doping and structure / T_c-Aenderungen von R_1_-_yCa_yBa_2Cu_3O_x unter hohem Druck: Einfluss von Dotierung und Struktur
- Authors
- Publication Date
- Jan 01, 2003
- Source
- OpenGrey Repository
- Keywords
- Language
- German
- License
- Unknown
Abstract
The transition temperature to superconductivity, T_c, of the high-temperature superconductor R_1_-_yCa_yBa_2Cu_3O_x (R=Y, Nd) can easily be changed by variation of oxygen or calcium content. Exposing the sample to hydrostatic pressure leads to additional T_c changes depending on the oxygen and calcium content. In this work possible origins of the T_c changes under hydrostatic pressure and the role of doping and structural aspects will be discussed. Like many other superconducting properties the pressure effect dT_c/dp is strongly depending on the hole concentration n_h in the CuO_2 planes. In the underdoped region the pressure effect of R_1_-_yCa_yBa_2Cu_3O_x is positive and can reach values up to 7 K/GPa. In the optimally doped and overdoped region all R_1_-_yCa_yBa_2Cu_3O_x systems show the same linear decreasing dT_c/dp(n_h) dependence. For n_h > 0.175 the dT_c/dp values are even negative. It will be shown that the dT_c/dp(n_h)-dependence with a pressure effect maximum in the underdoped region can be qualitatively described by pressure induced charge transfer from the CuO chains to the CuO_2 planes especially in the underdoped region, however, additional effects besides charge transfer increase T_c under hydrostatic pressure. In the light of the model of pressure induced depinning of spin-charge stripes it becomes clear why non-charge transfer effects lead to large T_c variations under pressure especially in the underdoped regime and why these non-charge transfer effects differ strongly from system to system. (orig.) / SIGLE / Available from TIB Hannover: ZA 5141(6821) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische Informationsbibliothek / DE / Germany
