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arXiv · 2202.02577

Long-wavelength phonon dynamics in incommensurate Bi2Sr2CaCu2O(8+delta) crystals by Brillouin light scattering spectroscopy

Bradley D. E. McNiven·James P. F. LeBlanc·Gordon T. Andrews
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Abstract

Room temperature phonon dynamics in crystals of the high-Tc superconductor Bi2Sr2CaCu2O(8+delta) were probed using Brillouin light scattering spectroscopy. Eight distinct acoustic modes were observed and identified, including two quasi-longitudinal bulk modes and four quasi-transverse bulk modes. A peak at a frequency shift of ~95 GHz with behaviour reminiscent of an optic phonon was also observed in the spectra. The existence and nature of these modes is a manifestation of the incommensurate structure of Bi2Sr2CaCu2O(8+delta) and suggests that it may be categorized as a so-called composite incommensurate crystal comprised of two weakly interacting sublattices. A mass ratio of m1/m2=0.36 obtained from the two measured quasi-longitudinal acoustic velocities led to sublattice assignments of Bi2Sr2O4 and CaCu2O4. The Brillouin data also places an upper limit of ~10 GHz on the crossover frequency between commensurate and incommensurate phonon dynamics.

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Bradley D. E. McNiven, James P. F. LeBlanc, Gordon T. Andrews. 2022-02-05. Long-wavelength phonon dynamics in incommensurate Bi2Sr2CaCu2O(8+delta) crystals by Brillouin light scattering spectroscopy. https://doi.org/10.1103/physrevb.106.054113

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