Fig. 3: Electron-phonon coupling in Ag@Au hybrids.
a Electron-phonon coupling constant (λ) estimated from point contact measurements and electrical transport (ρ − T) data as function of Ag filling F. Error bars in the open and filled points, representing λ have been estimated from the error in resistivity, ρ, shown in Fig. 1g by error propagation. b Room temperature resistivity (ρ300 K) for different materials is normalized by the respective Mott-Ioffe-Regel resistivity (ρMIR) and plotted as a function of electron-phonon coupling constant, λ. Red, blue, green, and yellow open circles represent non-superconducting metals, metals/alloys that superconduct at low T, intermetallic compounds, and high-Tc cuprates, respectively (see Supplementary Information VIII for detail). Filled red and purple circles represent films of pure Au nanoparticle and Ag@Au hybrids for different F values, respectively. c (Top Panel): A schematic of the electrochemical potential of electrons at the Ag and Au sites across the Ag@Au nanohybrid, ϵ0 being the potential difference between them. Electrons transfer from a higher onsite potential at Ag to a lower potential in Au. (Bottom Panel): Theoretical computation of the excess electron occupancy, δn in a square lattice toy model (See Methods and Supplementary Information Section IX), where Ag is embedded inside Au. d Binding energy peak of the Au-4f5/2 peak from X-ray photoelectron spectroscopy (XPS) is shown for two different values of F = 0.11, 0.5. The data is shifted vertically for clarity. (See Fig. S5 and Section II.B in Supplementary Information for more details). The dotted line represents the binding energy peak of Au-4f5/2 core-level of Au0. Inset shows the theoretically computed EPC on the square lattice toy model, λ(calc) with the average excess electron occupancy (〈δnAu〉) on Au.
