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Giant phonon anomalies in the bond-stretching branches in Ba_0.6K_0.4BiO_3

M. Braden·W. Reichardt·S. Shiryaev·S. N. Barilo
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Abstract

The dispersion of the longitudinal bond-stretching (BS) branches in superconducting Ba0.6K0.4BiO3 (BKBO) studied by inelastic neutron scattering reveals giant phonon anomalies. In the [110] and [111] directions these branches even split close to the middle of the zone, in contradiction to any harmonic lattice dynamical model with cubic symmetry. The additional low energy branch in the [111] direction ends at the R-point with a frequency near 10.5THz representing a doping induced renormalization of a breathing type vibration by about 40%, the strongest observed so far in any superconductor.

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M. Braden, W. Reichardt, S. Shiryaev, S. N. Barilo. 2001-07-24. Giant phonon anomalies in the bond-stretching branches in Ba_0.6K_0.4BiO_3. https://arxiv.org/abs/cond-mat/0107498

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