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Double-valued strong-coupling corrections to Bardeen–Cooper–Schrieffer ratios

2020/06/19 by E. F. Talantsev, E F Talantsev · 2 citations
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #BCS theory #Dimensionless quantity #High-pressure geophysics and materials #High-temperature superconductivity #Inorganic Chemistry and Materials #Inorganic Fluorides and Related Compounds #Logarithm #Pairing #Superconductivity #cond-mat.supr-con

paper · pdf · doi:10.1088/1361-6668/abbb19

published in Superconductor Science and Technology 33(12), 124003 (IOP Publishing) · 22 pages, 8 figures

arxiv created 2020/06/19 · openalex created_date 2020/06/19 · openalex publication_date 2020/09/23 · arxiv updated 2020/11/10 · openalex updated_date 2026/08/05

Abstract

Abstract The experimental discovery of near-room-temperature (NRT) superconductivity in highlycompressed H 3 S, LaH 10 and YH 6 has restored fundamental interest in the electron–phonon pairing mechanism in superconductors. One of the prerequisites of phonon-mediated NRT superconductivity in highly compressed hydrides is strong electron–phonon interactions, which can be quantified by dimensionless ratios of the Bardeen–Cooper–Schrieffer (BCS) theory vs <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>k</mml:mi> <mml:mi>B</mml:mi> </mml:msub> </mml:mrow> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:mrow> </mml:mrow> </mml:mfenced> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>ℏ</mml:mi> <mml:mrow> <mml:msub> <mml:mi>ω</mml:mi> <mml:mrow> <mml:mi>l</mml:mi> <mml:mi>n</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:mfenced> </mml:math> variable, where T c is the critical temperature and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>ω</mml:mi> <mml:mrow> <mml:mi>l</mml:mi> <mml:mi>n</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> is the logarithmic phonon frequency (Mitrovic et al 1984 Phys. Rev. B 29 184). However, all known strong-coupling correction functions for the BCS ratios are applicable for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>k</mml:mi> <mml:mi>B</mml:mi> </mml:msub> </mml:mrow> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:mrow> </mml:mrow> </mml:mfenced> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>ℏ</mml:mi> <mml:mrow> <mml:msub> <mml:mi>ω</mml:mi> <mml:mrow> <mml:mi>l</mml:mi> <mml:mi>n</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:mfenced> </mml:math> &lt; 0.20, which is not a high enough <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>k</mml:mi> <mml:mi>B</mml:mi> </mml:msub> </mml:mrow> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:mrow> </mml:mrow> </mml:mfenced> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>ℏ</mml:mi> <mml:mrow> <mml:msub> <mml:mi>ω</mml:mi> <mml:mrow> <mml:mi>l</mml:mi> <mml:mi>n</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:mfenced> </mml:math> range for NRT superconductors, because the latter exhibit variable values of 0.13 &lt; <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>k</mml:mi> <mml:mi>B</mml:mi> </mml:msub> </mml:mrow> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:mrow> </mml:mrow> </mml:mfenced> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>ℏ</mml:mi> <mml:mrow> <mml:msub> <mml:mi>ω</mml:mi> <mml:mrow> <mml:mi>l</mml:mi> <mml:mi>n</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:mfenced> </mml:math> &lt; 0.32. In this paper, we reanalyze the full experimental dataset (including data for highly compressed H 3 S) and find that the strong-coupling correction functions for the gap-to-critical-temperature ratio and for the specific-heat-jump ratio are double-valued nearly linear functions of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mrow> <mml:msu

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