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Hoesch, M.*; Fukuda, Tatsuo; Mizuki, Junichiro; Takenouchi, Tomohiro*; Kawarada, Hiroshi*; Sutter, J. P.*; Tsutsui, Satoshi*; Baron, A. Q. R.*; Nagao, Masanori*; Takano, Yoshihiko*
Physical Review B, 75(14), p.140508_1 - 140508_4, 2007/04
Times Cited Count:35 Percentile:77.53(Materials Science, Multidisciplinary)We observed phonon dispersions using inelastic X-ray scattering from CVD-grown high quality superconducting (=4.2 K) boron-doped and non-doped diamonds. By comparing these two, we found almost no change in the acoustic branch along both [111] and [001] directions. On the other hand, strong softening were observed in the optical branch of the boron-doped diamond in both directions: about 2 meV at Brillouin zone boundary and 8 meV at zone center ( point). From this result we estimated the electron-phonon coupling factor =0.33, and this supports theoretical models suggesting a phonon-mediated pairing mechanism via coupling of optical phonon modes to Fermi surfaces around the point.
Fukuda, Tatsuo; Hoesch, M.*; Takenouchi, Tomohiro*; Sutter, J. P.*; Tsutsui, Satoshi*; Baron, A.*; Nagao, Masanori*; Takano, Yoshihiko*; Kawarada, Hiroshi*; Mizuki, Junichiro
no journal, ,
Diamond is well known for its maximum hardness, large energy gap, high thermal conductivity, and so on. In addition to these, the superconductivity was discovered recently in boron doped (B-doped) diamond, and this was soon confirmed by other groups. We performed inelastic X-ray scattering experiments at BL35XU of SPring-8 to measure phonons in a highly B-doped CVD grown diamond having superconducting transition at 4.2 K. By comparing the experimental results with those from nitrogen doped CVD grown diamond and/or pure diamond, we found that the optical modes are softened especially at around the Brillouin zone center along with a strong broadening, while the acoustic modes do not show both softening and broadening. This confirms the strong electron-phonon coupling in superconducting diamond.