Spectroscopy of quasiparticle excitations of superconducting bismuth cuprate at high pressures |
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Authors: | V M Svistunov V Yu Tarenkov A I D’yachenko R Aoku H Murakami M Shirai |
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Institution: | (1) A. A. Galkin Donetsk Physicotechnical Institute, Ukrainian National Academy of Sciences, 340114 Donetsk, Ukraine;(2) College of Industrial Technology, Amagasaki Nishi-Koya, Japan;(3) Osaka University, Japan |
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Abstract: | We study the energy spectrum of Bi2223 (Bi1.6Pb0.4Sr1.8Ca2.2Cu3Ox) at high hydrostatic pressures by Andreev-and tunneling-spectroscopy methods. We determine the gap anisotropy in the basal
ab plane and find the following values for the parameters Δ(ϕ): Δmax=42 mV, and Δmin=19.5 mV (T
c
=110 K and dT
c
/dP=0.16 K/kbar). We detect an increase in the ratio R=2Δmax/kT
c
with pressure P; for Bi2223 cuprate, dR/dP≈0.017 kbar−1. In the phonon-frequency region we detect a “softening,” due to pressure, of the high-frequency part of the phonon spectrum
corresponding to “breathing” modes of oxygen, as well as other optical modes of Cu-O. The characteristic frequencies of the
spectrum for ℏΩ>60 mV are found to decrease, with increasing pressure, at a rate d ln(ℏΩ)/dP≈−6.5±0.5×10−3 kbar−1. This result explains the observed increase in the ratio 2Δ/kT
c
(P) in the model of strong electron-phonon interaction.
Zh. éksp. Teor. Fiz. 113, 1397–1410 (April 1998) |
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Keywords: | |
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