Influence of Pressure on the Electron-Phonon Interaction in Superconductors

Mat. Orendáča,b, S. Gabáni a, G. Pristáš a, E. Gažo a, N. Shitsevalova c, and K. Flachbart a aInstitute of Experimental Physics, SAS, Watsonova 47, 040 01 Košice, Slovakia bInstitute of Physics, Faculty of Sciences, P.J. Safarik University, Park Angelinum 9, 040 01 Košice, Slovakia cInstitute for Problems of Materials Science, NASU, Krzyzhanovsky 3, 036 80 Kiev, Ukraine

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The electron-phonon interaction is a very important and ubiquitous process in solids, affecting almost all their physical properties. In metals, where the relaxation processes depend on both electrons and phonons, all thermodynamic and transport properties are dictated by the electron-phonon interaction. A very strong manifestation of the electron-phonon interaction is related with the superconducting state. Here we report the effect of high pressure on the transport electron-phonon interaction, λtr, in superconducting systems such as YB6 (Tc ≈ 7.5 K), Pb (Tc ≈7.2 K), Nb bulk or thin film (Tc ≈9.2 K), and in LaB6 in which superconductivity was not yet observed. The expected pressure effect should correspond to the theoretically predicted negative pressure effect on Tc (except for Nb thin film and LaB6). To determine the influence of pressure on λtr, we utilized the Bloch-Grüneisen fit (denoted also as "thermal spectroscopy") of the precise temperature dependence of resistivity measurements in the normal state up to a pressure of 2.8 GPa. Based on this fit the observed negative pressure effect on λtr values, dλtr/dp, are as follows: dλtr/dp ≈-0.045 GPa-1 for YB6, dλtr/dp ≈-0.13 GPa-1 for Pb, dλtr/dp ≈-0.019 GPa-1 or -0.028 GPa-1 for Nb bulk or thin film, respectively, and dλtr/dp ≈-0.003 GPa-1 for LaB6.

DOI: 10.12693/APhysPolA.131.1039 PACS numbers: 74.70.Ad, 72.15.Eb, 74.62.Fj, 74.25.F-, 63.20.kd