Progress in Superconductivity and Cryogenics (한국초전도ㆍ저온공학회논문지)

The Korean Society of Superconductivity and Cryogenics (한국초전도저온학회)
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Investigation on the phonon behavior of MgB2 films via polarized Raman spectra

  • R. P. Putra (Department of Physics, Chungbuk National University) ;
  • J. Y. Oh (Department of Physics, Chungbuk National University) ;
  • G. H. An (Department of Physics, Chungbuk National University) ;
  • H. S. Lee (Department of Physics, Chungbuk National University) ;
  • B. Kang (Department of Physics, Chungbuk National University)
  • Received : 2024.03.07
  • Accepted : 2024.03.29
  • Published : 2024.03.31
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Abstract

In this study, we explore the anisotropy of electron-phonon coupling (EPC) constant in epitaxially grown MgB2 films on c-axis oriented Al2O3, examining its correlation with the critical temperature (Tc) and local structural disorder assessed through polarized Raman scattering. Analysis of the polarized Raman spectra reveals angle-dependent variations in the intensity of the phonon spectra. The Raman active mode originating from the boron plane, along with two additional phonon modes from the phonon density of states (PDOS) induced by lattice distortion, was distinctly observed. Persistent impurity scattering, likely attributed to oxygen diffusion, was noted at consistent frequencies across all measurement angles. The EPC values derived from the primary Raman active phonon do not significantly vary with changing observation angles, followed by that the Tc values calculated using the Allen and Dynes formula remain relatively constant across all polarization angles. Although the E2g phonon mode plays a crucial role in the EPC mechanism, the determination of Tc values in MgB2 involves not only electron-E2g coupling but also contributions from other phonon modes.

Keywords

Acknowledgement

This work was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2021R1I1A3044518)

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