Elastic Moduli and Electron-Phonon Coupling Constant of NdBa2Cu3-xFexO7-δ Superconductor
Modulus Kekenyalan dan Pemalar Gandingan Elektron-Fonon Superkonduktor NdBa2Cu3-xFexO7-δ
Abd-Shukor R. Chew C.M. Tang M.S. Nor-Azah N.J. Chiu W.S. Chen S.K. Nasir M.N.M. Uskenbaev D.
February 2026Penerbit Universiti Kebangsaan Malaysia
Sains Malaysiana
2026#55Issue 2327 - 337 pp.
The ultrasonic method is very sensitive in determining the role of phonons in the mechanism of superconductivity. In this research, the longitudinal velocity, vL and shear velocity, vs for NdBa2Cu3-xFexO7-δ superconductors with x = 0, 0.02 and 0.05 have been measured between 80 K and around 220 K at a frequency of 10 MHz. NdBa₂Cu₃O₇ exhibited an onset transition temperature, Tc-onset of 93 K and the x = 0.02 sample showed Tc-onset of 58 K while the x = 0.05 showed no transition temperature. The longitudinal and shear velocities increased monotonically with decreasing temperature down to 80 K. The Debye temperature, θD, decreased with Fe doping. For NdBa2Cu3, θD is 370 K, while for the Fe-doped samples it is reduced to 314 K (x = 0.02) and 265 K (x = 0.05), respectively. This decrease showed lattice softening when the superconducting property was suppressed. The electron-phonon coupling constant of NdBa2Cu3 according to the weak coupling limit of the BCS theory is λBCS = 0.67, while in the two-dimensional van Hove scenario, λvH2 = 0.023. For the x = 0.02 sample, λBCS = 0.55 and λvH2 = 0.020. These λvH2 values are consistent with the measured values reported in superconducting cuprates reported by other researchers. This work showed that the electron-phonon coupling together with the infinite density of states at the Fermi level as suggested in the two-dimensional van Hove scenario can be used to explain high temperature superconductivity in the NdBa2Cu3 superconductor.
Debye temperature , longitudinal velocity , shear velocity , van Hove scenario
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Department of Applied Physics, Universiti Kebangsaan Malaysia, UKM, Selangor, Bangi, 43600, Malaysia
Pusat PERMATA@Pintar Negara, Universiti Kebangsaan Malaysia, UKM, Selangor, Bangi, 43600, Malaysia
Low Dimensional Materials Research Centre, Department of Physics, Faculty of Science, Universiti Malaya, Kuala Lumpur, 50603, Malaysia
Department of Physics, Universiti Putra Malaysia, UPM, Selangor, Serdang, 43400, Malaysia
Institute of Energy, S. Seifullin Kazakh Agrotechnical Research University, Astana, Kazakhstan
Department of Applied Physics
Pusat PERMATA@Pintar Negara
Low Dimensional Materials Research Centre
Department of Physics
Institute of Energy
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