Electron-phonon coupling and spin fluctuations in the Ising superconductor NbSe2

Journal Article · Wed Apr 26 00:00:00 UTC 2023 · npj Computational Materials

DOI: https://doi.org/10.1038/s41524-023-01017-4 · OSTI ID:1971579

Das, S. ; Paudyal, H. ; Margine, E. R.; Agterberg, D. F. ; Mazin, I. I.

Abstract Ising superconductivity, observed in NbSe ₂ and similar materials, has generated tremendous interest. Recently, attention was called to the possible role that spin fluctuations (SF) play in this phenomenon, in addition to the dominant electron–phonon coupling (EPC); the possibility of a predominantly triplet state was discussed and led to a conjecture of viable singlet–triplet Leggett oscillations. However, these hypotheses have not been put to a quantitative test. In this paper, we report first principle calculations of the EPC and also estimate coupling with SF, including full momentum dependence. We find that: (1) EPC is strongly anisotropic, largely coming from the $$$$K-{K}^{{\prime} }$$$$ $K-K^{\prime }$ scattering, and therefore excludes triplet symmetry even as an excited state; (2) superconductivity is substantially weakened by SF, but anisotropy remains as above; and, (3) we do find the possibility of a Leggett mode, not in a singlet–triplet but in an s ₊₊ – s _± channel.

• Research Organization: Univ. of Wisconsin, Madison, WI (United States)
• Sponsoring Organization: National Science Foundation (NSF); US Department of the Navy, Office of Naval Research (ONR); USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE)
• Grant/Contract Number: SC0021971
• OSTI ID: 1971579
• Journal Information: npj Computational Materials, Journal Name: npj Computational Materials Journal Issue: 1 Vol. 9; ISSN 2057-3960
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United Kingdom
• Language: English