Pressure-enabled phonon engineering in metals

Abstract

We present a combined first-principles and experimental study of the electrical resistivity in aluminum and copper samples under pressures up to 2 GPa. The calculations are based on first-principles density functional perturbation theory, whereas the experimental setup uses a solid media piston-cylinder apparatus at room temperature. We find that upon pressurizing each metal, the phonon spectra are blue-shifted and the net electron-phonon interaction is suppressed relative to the unstrained crystal. This reduction in electron-phonon scattering results in a decrease in the electrical resistivity under pressure, which is more pronounced for aluminum than for copper. We show that density functional perturbation theory can be used to accurately predict the pressure response of the electrical resistivity in these metals. This work demonstrates how the phonon spectra in metals can be engineered through pressure to achieve more attractive electrical properties.density functional theory | electron-phonon coupling | high-pressure conductivity S train has proven to be an effective means of modifying the electronic structure in semiconducting materials, particularly band gap modulation in metal-oxide-semiconductor field-effect transistors (1-6). Strain also affects the phonon structure and transport properties of metals, which have no band gap to modulate, and may be used to engineer more attractive electrical properties at both the macroscale and the nanoscale.The nonzero electrical resistivity of a metal has two main contributions: the presence of defects and the vibrations of the lattice atoms about their equilibrium sites (7). Scattering events between electrons and vibrational quanta (phonons) give rise to the finite electrical resistivity in pure samples. First-principles calculations have proven to be remarkably successful in giving accurate descriptions of the phonon-induced electrical resistivity in metals (8-10). It also has been shown that the phonon-mediated properties, including the electrical resistivity and the superconducting transition temperature, can be altered under pressure (11-13). It has been suggested that the electrical transport properties due to the electron-phonon interaction in aluminum show a particularly strong response to interatomic spacing, particularly when the system is subject to extreme quantum confinement (14,15).Studies of the effect of pressure on the superconducting properties of aluminum suggest that superconductivity is suppressed through a reduction in the critical temperature, T c , as the pressure is increased (11,12,(16)(17)(18). It also has been reported that the electron-phonon coupling constant, λ, decreases in aluminum under pressure (11,16), but a quantitative extension to the electrical resistivity under pressure is lacking. Cheung and Ashcroft (13) suggested a decrease in the electrical resistivity of aluminum under volume compression by using a primitive pseudopotential model with experimentally determined interatomic force constants, but the pressures corresponding t...

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“…Any reduction in electron–phonon coupling will be reflected in a reduction in the electrical resistivity. [ 47 ] In other words, as copper's electron–phonon coupling ( λ ) decreases, so does its electrical resistivity (/conductivity) decreases (/increases). In our case, applying 0.15% strain reduces λ , and thus electrical resistivity ( ρ = 1/ σ ) decreases.…”

“…The copper's electrical resistivity (/conductivity) decreases (/increases) due to reducing electron-phonon coupling. [39,47] According to Wiedemann-Frantz law, EC is proportional to TC; thus, increasing EC enhances TC. [31] A similar result was observed by Giri et al, [39] who found that a small reduction in the electron-phonon coupling factor of metals enhanced electrical and electronic thermal conductivities largely.…”

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