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ASM Sci. J., 7(1), 18–22Electron-phonon Coupling Constants of TwodimensionalCopper Oxide-basedHigh Temperature SuperconductorsR. Abd-Shukor 1 * and W.Y. Lim 1The electron-phonon coupling constant of the copper oxide-based high temperature superconductors in thevan Hove scenario was calculated using three known models and by employing various acoustic data. Threeexpressions for the transition temperature from the models were used to calculate the constants. All threemodels assumed a logarithmic singularity in the density of states near the Fermi surface. The calculatedelectron-phonon coupling constant ranged from 0.06 to 0.28. The constants increased with the transitiontemperature indicating a strong correlation between electron-phonon coupling and superconductivity in thesematerials. These values were smaller than the values estimated for the conventional three-dimensional BCStheory. The results were compared with previous reports on direct measurements of electron-phonon couplingconstants in the copper oxide based superconductors.Key words: Acoustic methods; electron-phonon coupling constant; van Hove scenario; transition temperaturemodelsThe understanding of the mechanism of superconductivityin the cuprates has been one of the major challenges incondensed matter physics since the discovery of this classof superconductors many years ago. Several models havebeen proposed throughout the years. Basically there aretwo opposing views on the possible mechanism. The firstidea is based on the electron-phonon interaction and theother is based on the one-band Hubbard Hamiltonian. Theelectron-phonon interaction in the cuprates is said to be tooweak to produce a high T c . On the other hand, it is not easy toexplain the thermodynamic properties of the cuprates withpositive potential of the Hubbard model. A combination ofboth ideas to explain high T c superconductivity has beenreported recently (Szczesniak et al. 2012).Although the possible role of phonons in the cuprateshas been abandoned earlier on, the important role ofphonons in the pairing mechanism in the materials has Modelsregained attention in the past few years following a numberof experimental and theoretical evidences (Lanzara et al.2001; Reznik et al. 2006; Shimada et al. 2002). By takinginto consideration the singularity in the density of statesat the Fermi level for a two-dimensional system, recentworks have shown that such a model can be viable for high N Etemperature superconductivity (Newns et al. 1995).* Corresponding author (e-mail: ras@ukm.my)18A large effect can be produced near the van Hovesingularity even for arbitrarily weak interactions(Vozmediano et al. 2002). Hence in principle, a very smallelectron-phonon coupling is sufficient for the formation ofthe Cooper pairs. It is interesting to determine the value ofthe electron-phonon coupling constant in the cuprate. In aprevious paper we reported the electron-phonon couplingconstant in the cuprates for the van Hove scenario (Abd-Shukor 2007). In this paper we calculated the electronphononcoupling constant for the van Hove scenario derivedfrom three expression of the transition temperature (Getinoet al. 1993; Newns et al. 1992; Tsuei et al. 1990) and byusing parameters determined from acoustic methods. Theelectron-phonon coupling constants were then comparedto experimental results of direct measurements of theelectron-phonon coupling constant.The density of states at the Fermi level in the van Hovescenario is given as:( ) = N olnE FE E Ftanh E E F= E E F2k BT c2k BT c, (1)1 School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysiatanh E E F=12k BT cT c = 1.36(10 D )exp 2NoV + ln k B(10 D )k2112