Evidence for electron-electron interaction in topological insulator thin films

Abstract: We consider in our work high quality single crystal thin films of Bi2Se3, grown by molecular beam epitaxy, both with and without Pb doping. Our ARPES data demonstrate topological surface states with a Fermi level lying inside the bulk band gap in the Pb doped filims. Transport data show weak localization behavior, as expected for a 2D system, but a detailed analysis within the standard theoretical framework of diffusive transport shows that the temperature and magnetic field dependences of resistance cannot be reconciled in a theory that neglects inter-electron interactions. We demonstrate that an excellent account of quantum corrections to conductivity is achieved when both disorder and interaction are taken into account. These results clearly demonstrate that it is crucial to include electron electron interaction for a comprehensive understanding of diffusive transport in topological insulators.

• The paper shows that incorporating electron-electron interactions is essential to explain the transport phenomena observed in topological insulator thin films.
• Methodologies including ARPES and magnetoconductance measurements confirmed that Pb doping positions the Fermi level within the band gap, emphasizing surface state contributions.
• The research highlights that integrating disorder effects with electron interactions reconciles discrepancies in diffusive transport models, paving the way for improved electronic applications.

Insight into Electron-Electron Interactions in Topological Insulators

The paper "Evidence for electron-electron interaction in topological insulator thin films" presents a detailed investigation of electron-transport phenomena in thin films of Bi$_{2}$Se$_{3}$, including samples with Pb doping. These films are evaluated not only for their intrinsic topological surface states but also for the influence of electron-electron interactions (EEI) on their transport characteristics. The study stands out for its emphasis on the significance of interaction effects, which have often been inadequately considered in prior research on topological insulators (TIs).

Key Findings and Analysis

The researchers employed angle-resolved photoemission spectroscopy (ARPES) to confirm the presence of topological surface states, with the Fermi level positioned within the bulk band gap in Pb-doped films. This is a crucial observation, as it suggests a reduced contribution from the bulk states to the electronic transport, allowing for more pronounced effects from the surface states. The transport data displayed weak localization (WL) effects typically associated with two-dimensional systems, which were further deciphered through a robust theoretical framework that incorporated both disorder and interactions.

A central theme in the paper is that the standard model of diffusive transport, which often neglects inter-electron interactions, fails to thoroughly explain the observed experimental data. The temperature dependence and magnetoconductance measurements were inconsistent with models excluding EEI. When both disorder and electron-electron interactions were included, the analysis achieved an excellent correlation with the experimental quantum corrections to the conductivity. This finding underscores the pivotal role of EEI in shaping the transport properties of TIs.

Implications and Future Prospects

The implications of this research extend to both theoretical and practical realms. Theoretically, it asserts the necessity of incorporating interaction effects into models evaluating quantum transport in TIs. This could potentially reconcile discrepancies noted in earlier experimental studies which aligned poorly with non-interacting models. Practically, these insights may influence the way TIs are utilized in electronic devices, as understanding interaction effects is crucial for manipulating film conductivities effectively.

Furthermore, the inability to distinctly separate the contributions of bulk and surface states through transport measurements remains an open question. Despite demonstrating significant interaction effects, the analysis did not disentangle their distinct impacts on bulk versus surface conduction channels. Future research might focus on developing experimental techniques or analytical models that can more precisely differentiate these contributions.

Conclusion

In conclusion, this paper advances the comprehension of electron-electron interactions in topological insulators, especially under two-dimensional transport conditions. Its comprehensive approach—combining experimental data and theoretical modeling—provides a nuanced understanding of these systems, emphasizing EEI's role within the broader context of TI transport phenomena. Such insights are pertinent for future explorations in topological materials and for optimizing their integration into next-generation electronic applications.