Screening, Friedel oscillations and low-temperature conductivity in topological insulator thin films

Abstract

In thin topological insulator films, the top and bottom surfaces are coupled by tunneling, which restores backscattering and strongly affects screening. We calculate the dielectric function in the random phase approximation obtaining a closed-form result. Unlike independent TI surfaces, the dielectric function of thin films exhibits a valley as a function of wavenumber $q$ and tunneling, as well as a cusp at $q=2k_F$, with $k_F$ the Fermi wave vector. As a result of the cusp, Friedel oscillations decay with distance $r$ as $\sin (2k_{F}r)/(2k_{F}r{)}^2$. We determine the longitudinal conductivity $\sigma$ in the first Born approximation at low temperatures where screened impurities provide the dominant scattering mechanism. At high electron densities $n_e$, $\sigma \propto n_e$, while at low densities $\sigma \propto n_e^{3/2}$.

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• Optical responses and optical activity of ultrathin films of topological insulator
• Topological Effects on the Magnetoconductivity in Topological Insulators
• Anomalous Hall Coulomb drag of massive Dirac fermions
• Real-space dynamical mean-field theory of Friedel oscillations in strongly correlated electron systems
• Coulomb drag in topological insulator films
• Coulomb drag in topological materials
• Friedel oscillations in two-dimensional materials with inverted bands and Mexican-hat dispersion
• Signatures of non-local conductivity in near-field microscopy
• Spin-polarized scanning tunneling microscopy measurement scheme for determining the quantum geometric tensor
• Dynamical density response and collective modes of topological insulator ultra-thin films
• Unveiling Novel Resonant Interband Contribution to Polarizability in three-dimensional systems