Large Intrinsic Resistivity of Monolayer Cu₂Si and Fermi Surface Nesting

We perform the first-principles calculation on the intrinsic resistivity of monolayer (ML) Cu2Si limited by electron–phonon (e–ph) scattering. We find that the intrinsic resistivity (ρ) of ML Cu2Si is higher than that in lightly doped graphene by 2 orders of magnitude, though the two materials present close analogy in crystal and electron structures. There are two reasons for the sizable difference of intrinsic resistivity between ML Cu2Si and graphene. At first, ML Cu2Si has a much softer phonon than graphene. More importantly, in ML Cu2Si, the flexural phonon corresponding to the out-of-plane lattice vibration can couple to the electronic states of opposite parities strongly to realize the Fermi surface nesting (FSN) effect, whereas this kind of phonon in graphene is completely decoupled from e–ph interaction. In addition, our results show that the intrinsic resistivity is perfectly isotropic, and it begins to depend linearly on temperature (T) as T > 70 K, which is much lower than the estimated Debye temperature of 600 K. We find that such an untimely occurrence of a linear ρ–T relationship is tightly associated with the FSN effect of the multibranch Fermi surface realized by e–ph scattering.