Enormous enhancement of resistivity in nanostructured electron-phonon systems

TL;DR

This paper demonstrates that nanostructuring silver in a gold matrix significantly increases resistivity due to interface effects, modeled through a Holstein model with inhomogeneous electron-phonon coupling, revealing large enhancements in resistivity.

Contribution

The study introduces a model combining nanocluster configurations and inhomogeneous electron-phonon interactions to explain resistivity enhancements at interfaces.

Findings

Resistivity increases with Ag volume fraction.

Large linear T resistivity coefficient observed.

Interface inhomogeneity influences resistivity behavior.

Abstract

Recent experiments on nanoclusters of silver (Ag) embedded in a gold (Au) matrix reveal a huge increase in both the zero temperature resistivity and the coefficient of the ``$T$ linear'' thermal resistivity with increasing volume fraction of Ag. A fraction $f \sim 50\%$ of Ag leads to a factor of $20$ increase in the residual resistivity, and a $40$ fold enhancement in the coefficient of linear $T$ resistivity, with respect to Au. Since Au and Ag both have weak electron-phonon coupling we surmise that the huge enhancements arise from a moderately large electron-phonon coupling that may emerge at the Ag-Au interface. We construct nanocluster configurations for varying $f$ in two dimensions, define a Holstein model on it with weak coupling on the `interior' sites and a strong coupling on the interfacial sites, and solve the model through exact diagonalisation based Langevin dynamics. Computing the resistivity, we observe a large $T=0$ increase with $f$ and also a linear $T$ enhancement factor of $\sim 30$. While the enhancement factors are parameter choice dependent, our key qualitative result is that the interface physics is inhomogeneous, with widely varying distortions, and different segments of the interface dictate the residual resistivity and the thermal scattering.