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Pressure dependence of the upper critical field of MgB2 and of YNi2B2C

H. Suderow·V. G. Tissen·J. P. Brison·J. L. Martinez·S. Vieira·P. Lejay·S. Lee·S. Tajima
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Abstract

We present measurements of H$_{c2}(T)$ under pressure in MgB$_2$ and in YNi$_2$B$_2$C. The changes in the shape of H$_{c2}(T)$ are interpreted within current models and show the evolution of the main Fermi surface velocities $v_F$ and electron-phonon coupling parameters $λ$ with pressure. In MgB$_2$ the electron-phonon coupling strength of the nearly two dimensional $σ$ band, responsible for the high critical temperature, is more affected by pressure than the $π$ band coupling, and the hole doping of the $σ$ band decreases. In YNi$_2$B$_2$C, the peculiar positive curvature of H$_{c2}(T)$ is weakened by pressure.

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H. Suderow, V. G. Tissen, J. P. Brison, J. L. Martinez, S. Vieira, P. Lejay, S. Lee, S. Tajima. 2004-12-02. Pressure dependence of the upper critical field of MgB2 and of YNi2B2C. https://doi.org/10.1103/physrevb.70.134518

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