Ultrasonic and related experiments in high-T_csuperconductors

Abstract

The results of ultrasonic, sonic and infrasonic experiments in high-T, superconductors (HTSC) are reviewed. Some other related fieids of investigation are also mentioned.

Three-dimensional dispersion induced by extreme tensile strain inLa2−xSrxCuO4films

“…Our thinnest film, corresponding to 3.5 unit cells, had a c axis of 13.06 Å, i.e., a c-axis strain ⑀ c = −1.2% ͑compression͒. Using available data for the elastic moduli of LSCO, 8 one can estimate the corresponding inplane strain ⑀ ab = + 3.3% ͑for Poisson ratio Ϸ 0.2͒. This unusual huge in-plane expansion of the lattice coincides with the relative mismatch between the STO substrate and the LSCO film.…”

Vortex instability phase of Bi2Sr2CaCu2O8+y single crystal

“…This idea easily leads to the growing of the elasticity of vortices with decreasing current density j. This concept is supported by the experimental result of Chang et al, where the monotonic increasing of the longitudinal sound velocity was observed with decreasing temperature without phonon softening [16,17]. In the hopping region, the individual pancake vortices can move independently.…”

Epitaxially Induced Defects in Sr- and O-doped La2CuO4Thin Films Grown by MBE: Implications for Transport Properties

“…Unfortunately, the literature provides no values for the change in the lattice parameters under uniaxial pressure, but a simple estimate of the pressure (P) required under these conditions can be made when Young's modulus (Y = 191 GPa), Poisson's ratio (li = 0.315) for the '214' compound [44] and the relations Δc/c = Ρ/Y, Δα/α = -vP/V are known. Applying these relations leads to a required uniaxial pressure between 0.45 and 0.9 GPa, which will increase the in-plane lattice parameter by 0.01-0.02 Å, in agreement with the experimental data derived from measurements of the dislocation spacings (Fig.…”