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A comparison of two high‐pressure superconducting phases in yttrium
Author(s) -
Durajski Artur P.
Publication year - 2015
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201552180
Subject(s) - pseudopotential , condensed matter physics , bcs theory , superconductivity , critical field , coulomb , yttrium , context (archaeology) , pairing , physics , materials science , electron , quantum mechanics , oxide , metallurgy , paleontology , biology
Elemental yttrium under high pressure is discussed in the context of superconductivity with a phonon‐mediated pairing mechanism. In particular, the strong‐coupling Eliashberg theory of superconductivity is employed to determine the thermodynamic properties of two new phases hp 3 ’ P 3 1 21 and oF 16 ’ Fddd that Y may take at 97GPa. The comparative studies show that the critical value of the Coulomb pseudopotential equals 0.20 and 0.24 for hp 3 ’ P 3 1 21 and oF 16 ’ Fddd phases, respectively. This directly translates into a value of the energy gap at the Fermi level 2 Δ ( 0 ) ∈ { 6.92 , 6.66 } meV and the electron effective mass at the critical temperature m e ★ / m e ∈ { 2.752 , 2.423 } . Moreover, we proved that the dimensionless ratios connected with the critical temperature, the energy gaps, the specific heat, and the thermodynamic critical field are no longer universal and cannot be correctly described using the canonical Bardeen–Cooper–Schrieffer (BCS) theory due to the strong‐coupling and retardation effects existing in the investigated systems.