Collective acoustic electronic excitations in LaH10 as a factor in boosting of the critical temperature of superconducting transition

• Published in: SN applied sciences Vol. 4; no. 7; pp. 1 - 9
• Main Authors: Pashitskii, Ernst A., Pentegov, Vsevolod I., Semenov, Alexei V.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.07.2022; Springer
• Subjects: Acoustic plasmons; Applied and Technical Physics; Chemistry/Food Science; Earth Sciences; Engineering; Environment; Materials Science; Polarization operator; Rare-earth superhydrides; Research Article; Room-temperature superconductivity; Rare-earth superhydrides; Room-temperature superconductivity; Polarization operator; Acoustic plasmons
• ISSN: 2523-3963; 2523-3971
• DOI: 10.1007/s42452-022-05077-x

The nearly room-temperature superconductivity that had been predicted theoretically for lanthanum and yttrium superhydrides at megabar pressures has been recently achieved experimentally in several superhydride compounds, including lanthanum decahydride with T c of about 250 K under high pressure of about 150 GPa. Though superconductivity should be governed by the phonon mechanism in these compounds, which is evident due to the measured deuterium isotope effect in LaD 10 , we believe that the choice of small values of the effective Coulomb constant, used in theoretical calculations of the critical temperature, merits farther substantiation. We discuss the possibility for the collective acoustic electronic excitations (acoustic plasmons) to appear in the collective spectra of superhydrides thus facilitating the suppression of the Coulomb repulsion. In LaH 10 the conditions for such mechanism arise due to the hybridization of La 4 f and H 1 s states near the Fermi level in the vicinity of the L-point of the Brillouin zone. A simple model approximation for the resulting conducting band allows us to show that in a certain portion of quasimomentum space an acoustic branch should appear in the spectrum of the collective electronic excitations in LaH 10 , arguably reducing the effective Coulomb constant. Article highlights We discuss the possibility for the acoustic plasmons to appear in superhydrides and to influence the superconducting properties of these materials. Analytical expression (the “extended” Lindhard formula) is derived for the 3D polarization operator in the case of anisotropic uniaxial effective mass. The possible change of the Fermi energy due to a slight deviation from stoichiometry is shown to have a potential to facilitate higher T c in superhydrides.