Single particle relaxation time versus transport scattering time in a 2D graphene layer

TL;DR

This paper theoretically compares the single-particle relaxation time and transport scattering time in 2D graphene, revealing how their ratio varies with impurity separation and dielectric properties, and contrasting these findings with semiconductor structures.

Contribution

It provides a detailed theoretical analysis of relaxation and scattering times in graphene, highlighting their dependence on physical parameters and differences from semiconductor systems.

Findings

The ratio τ_t/τ_s increases with impurity separation and dielectric constant.

Significant differences are found between graphene and semiconductor 2D systems.

Quantitative comparison clarifies the impact of scattering mechanisms in graphene.

Abstract

We theoretically calculate and compare the single-particle relaxation time ($\tau_s$) defining quantum level broadening and the transport scattering time ($\tau_t$) defining Drude conductivity in 2D graphene layers in the presence of screened charged impurities scattering and short-range defect scattering. We find that the ratio $\tau_t/\tau_s$ increases strongly with increasing $k_F z_i$ and $\kappa$ where $k_F$, $z_i$, and $\kappa$ are respectively the Fermi wave vector, the separation of the substrate charged impurities from the graphene layer, and the background lattice dielectric constant. A critical quantitative comparison of the $\tau_t/\tau_s$ results for graphene with the corresponding modulation-doped semiconductor structures is provided, showing significant differences between these two 2D carrier systems.