Wang, B.; Bianconi, A.; Mackinnon, I.D.R.; Alarco, J.A. Superlattice Delineated Fermi Surface Nesting and Electron-Phonon Coupling in CaC6. Preprints2024, 2024041451. https://doi.org/10.20944/preprints202404.1451.v1
APA Style
Wang, B., Bianconi, A., Mackinnon, I.D.R., & Alarco, J.A. (2024). Superlattice Delineated Fermi Surface Nesting and Electron-Phonon Coupling in CaC6. Preprints. https://doi.org/10.20944/preprints202404.1451.v1
Chicago/Turabian Style
Wang, B., Ian D. R. Mackinnon and Jose A. Alarco. 2024 "Superlattice Delineated Fermi Surface Nesting and Electron-Phonon Coupling in CaC6" Preprints. https://doi.org/10.20944/preprints202404.1451.v1
Abstract
The superconductivity of CaC6 as a function of pressure and of abundant Ca isotopes is revisited using DFT calculations on a 2c – double hexagonal superlattice. The introduction of superlattices is motivated by previous synchrotron absorption and Raman spectroscopy results on other superconductors that show evidence of superlattice vibrations at low (THz) frequencies. A 2c superlattice for CaC6 is illustrative of atomic orbital symmetry and periodicity, including bonding and antibonding s-orbital character implied by cosine modulated electronic bands. Inspection of the cosine band reveals that the cosine function has a small (meV) energy difference between bonding and antibonding regions relative to a midpoint non-bonding energy. Fermi surface nesting is apparent in an appropriately folded Fermi surface using a superlattice construct. Nesting relationships identify phonon vectors for conservation of energy and for phase coherency between coupled electrons at opposite sides of the Fermi surface. Detailed analysis of this Fermi surface nesting provides accurate estimates of the superconducting gaps for CaC6 with change in applied pressure. Recognition of superlattices within a rhombohedral or hexagonal representation provides consistent mechanistic insight on superconductivity and electron−phonon coupling in CaC6.
Chemistry and Materials Science, Materials Science and Technology
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