Effect of repulsion on superconductivity at low density

Journal Article · 27 February 2022 · Physical Review. B

DOI: https://doi.org/10.1103/physrevb.105.064518 · OSTI ID:1979719

Phan, Dan  ^[1]; Chubukov, Andrey V.  ^[2]

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1. University of Minnesota, Minneapolis, MN (United States); OSTI
2. University of Minnesota, Minneapolis, MN (United States)

Here we examine the effect of repulsion on superconductivity in a three-dimensional system with a Bardeen-Pines-like interaction in the low-density limit, where the chemical potential μ is much smaller than the phonon frequency ω_L. We parametrize the strength of the repulsion by a dimensionless parameter f, and find that the superconducting transition temperature T_c approaches a nonzero value in the μ = 0 limit as long as f is below a certain threshold f^*. In this limit, we find that T_c goes to zero as a power of f^* - f, in contrast to the high density limit, where T_c goes to zero exponentially quickly as f approaches f^*. For all nonzero f, the gap function Δ(ω_m) changes sign along the Matsubara axis, which allows the system to partially overcome the repulsion at high frequencies. We trace the position of the gap node with f and show that it approaches zero frequency as f approaches f^*. To investigate the robustness of our conclusions, we then go beyond the Bardeen-Pines model and include full dynamical screening of the interaction, finding that T_c still saturates to a nonzero value at μ = 0 when f < f^*.

• Research Organization: University of Minnesota, Minneapolis, MN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0014402
• OSTI ID: 1979719
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 6 Vol. 105; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English