Influence of Ca Content on Binding Energy and Cooper Pairing in Y_1-xCa_xBa₂Cu₃O_7-δ Compound

Bassam M. Mustafa^*, Abbas H. Rostam

Department of Physics, College of Science, Mosul University, Mosul, Iraq.

DOI: 10.4236/wjcmp.2015.51003                

Abstract

In this research, the influence of calcium content on the binding energy and Cooper pairing is investigated for the high temperature superconducting Y_1-xCa_xBa₂Cu₃O_7-δ compound where x = 0 - 0.2). This is done by using model considering that the formation of Cooper pairs happens during tunneling mechanism of holes between the two CuO₂ layers in the YCBCO crystal which are considered as forming adjacent potential wells. In this work, we make some modifications on the mentioned model and a modified equation for the binding energy as a function of Ca concentration is formulated to study the effect of Ca content by considering the change in the distance between the CuO₂ layer as a function of Ca. The calculated results agree very well with experimental results. This happens because the Ca²⁺ substitution for Y³⁺ leads to decreasing the distance between the two CuO₂ layers and hence potential energy of the system will be decreased. This leads to decreasing the binding energy between the Cooper pairs, and decreasing the distance between the two CuO₂ layers increasing the tunneling probability of holes between the two CuO₂ layers and thus increasing conduction mechanism and thus increasing current density, but this will decrease the energy gap and as a result decrease the critical temperature. The calculated results agree very well with experimental results.

Keywords

Superconductor Binding Energy, Formation of Cooper Pairing, Cooper Pairing in HTSC

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Anderson, P.W. (1987) The Resonating Valence Bond State in La2CuO4 and Superconductivity. Science, 235, 1196-1198. http://dx.doi.org/10.1126/science.235.4793.1196
[2]	Orenstein, J. and Millis, A.J. (2000) Advances in the Physics of High-Temperature Superconductivity. Science, 288, 468-474. http://dx.doi.org/10.1126/science.288.5465.468
[3]	Yang, H.-B., et al. (2008) Emergence of Preformed Cooper Pairs from the Doped Mott Insulating State in Bi2Sr2CaCu2O8+δ. Nature, 456, 77-80. http://dx.doi.org/10.1038/nature07400
[4]	Ruan, W. (2013) High Temperature Superconductivity: Cooper Pairs in Trap. arXiv:1306.3547.
[5]	Eun, J., Jia, X. and Chakravarty, S. (2010) Quantum Oscillations in Electron-Doped High-Temperature Superconductors. Physical Review B, 82, Article ID: 094515.
[6]	Tavkhelidze, A. (2010) Possible Mechanism of Cooper Pairing in Cuprates. arXiv:0807.0889.
[7]	Mourachkine, A. (2004) Room-Temperature Super Conductivity. Cambridge International Science Publishing, Cambridge.
[8]	You, L.X., Yurgens, A., Winkler, D., Lin, C.T. and Liang, B. (2005) Controlling the Intrinsic Josephson Junction Number in a Bi2Sr2CaCu2O8+δ Mesa. Journal of Applied Physics, 98, Article ID: 033913.
[9]	Giri, R., Singh, H.K., Srivastava, O.N., Awana, V.P.S., Gupta, A., Kumaraswamy, B.V. and Kishan, H. (2005) Effect of Ca Doping for Y on Structural/Microstructural and Superconducting Properties of . Physica C: Superconductivity and Its Applications, 419, 101-108. http://dx.doi.org/10.1016/j.physc.2005.01.002
[10]	Bottgery, G., Kaldisz, M.E., Fischery, P., Krugerz, Ch. and Fauth, F. (1996) The Influence of Ca Doping on the Crystal Structure and Superconductivity of Orthorhombic YBa2Cu3O7-δ. Journal of Physics: Condensed Matter, 8, 8889-8905. http://dx.doi.org/10.1088/0953-8984/8/45/021
[11]	Tavkhelidze, A. (2009) Large Enhancement of the Thermoelectric Figure of Merit in a Ridged Quantum Well. Nanotechnology, 20, Article ID: 405401. http://dx.doi.org/10.1088/0957-4484/20/40/405401
[12]	Khoshnevisan, B. (2002) Diffraction Studies of the Structural Phase Transition in the High Temperature Superconductor YBCO. Thesis, University of Salford, Salford.
[13]	Mustafa, B.M. and Rostam, A.H. (2014) The Influence of Ca Content on the Current Density of the Superconducting Compound. Journal of Superconductivity and Novel Magnetism, 27.
[14]	Mustafa, B.M. and Rostam, A.H. (2014) Investigating Effect of Ca Content on Electrostatic Potential Energy (EP), Critical Temperature and Structure Parameters on . Superconductor, under Publication.