R. C. Mataira | Searcharxiv

arXiv2020

Cooper pair trajectories in superconducting slab at self-field conditions

Dissipative-free electric current flow is one of the most fascinating and practically important property of superconductors. Theoretical consideration of the charge carriers flow in infinitely long rectangular slab of superconductor in the absence of external magnetic field (so called, self-field) is based on an assumption that the charge carriers have rectilinear trajectories in the direction of the current flow whereas the current density and magnetic flux density are decaying towards superconducting slab with London penetration depth as characteristic length. Here, we calculate charge particle trajectories (as single electron/hole, as Cooper pair) at self-field conditions and find that charge carriers do not follow intuitive rectilinear trajectories along the slab surface, but instead ones have meander shape trajectories which cross the whole thickness of the slab. Moreover, if the particle velocity is below some value, the charge moves in opposite direction to nominal current flow. This disturbance of the canonical magnetic flux density distribution and backward movement of Cooper pairs can be entire mechanism for power dissipation in superconductors.

cond-mat.supr-con↗

arXiv2019

Classifying superconductivity in ThH-ThD superhydrides/superdeuterides

Satterthwaite and Toepke (1970 Phys. Rev. Lett. 25 741) discovered that Th4H15-Th4D15 superhydrides are superconducting but exhibit no isotope effect. As the isotope effect is a fundamental prediction of electron-phonon mediated superconductivity described by Bardeen, Cooper, and Schrieffer (BCS) its absence alludes to some other mechanism. Soon after this work, Stritzker and Buckel (1972 Zeitschrift für Physik A Hadrons and nuclei 257 1-8) reported that superconductors in the PdHx-PdDx system exhibit the reverse isotope effect. Yussouff et al (1995 Solid State Communications 94 549) extended this finding in PdHx-PdDx-PdTx systems. Renewed interest in hydrogen- and deuterium-rich superconductors is driven by the discovery of near-room-temperature superconductivity in highly-compressed H3S (Drozdov et al. 2015 Nature 525 73) and LaH10 (Somayazulu et al 2019 Phys. Rev. Lett. 122 027001) as well as two recently discovered high-pressure hydrogen-rich phases of ThH9 and ThH10 (Semenok et al 2019 Materials Today, DOI: 10.1016/j.mattod.2019.10.005). We conclude that all known thorium super-hydrides/deuterides, to date, are unconventional superconductors - along with the heavy fermions, fullerenes, pnictides, cuprates, where we find they have Tc/Tf ratios within a range of of 0.008 < Tc/Tf < 0.120, where Tc is the superconducting transition temperature and Tf is the Fermi temperature.

cond-mat.supr-con↗