Abstract
The use of topological edge states for spintronic applications could be severely hampered by limited lifetimes due to intrinsic many-body interactions, in particular electron-phonon coupling. Previous works to determine the intrinsic coupling strength did not provide a coherent answer. Here, the electron-phonon interaction in the metallic surface state of 3D topological insulators is revised within a first principles framework. For the archetypical cases of Bi2Se3 and Bi2Te3, we find an overall weak coupling constant of less than 0.15, but with a characteristic energy dependence. Derived electronic self-energies compare favorably with previous angle-resolved photoemission spectroscopy results. The prevailing coupling is carried by optical modes of polar character, which is weakly screened by the metallic surface state and can be reduced by doping into bulk bands. We do not find any indication of a strong coupling to the A1g mode or the presence of a Kohn anomaly in the surface phonon spectrum. The weak intrinsic electron-phonon coupling guarantees long-lived quasiparticles at elevated temperatures.
Highlights
The remarkable feature of 3D topological insulators like Bi2Se3 is the existence of metallic surface states with a Dirac-like dispersion
More indirect information about electron-phonon interaction (EPI) was extracted from transport measurements[17, 18] and optical spectroscopy[19, 20]
To gain further insight into the microscopic nature of the EPI, we identified the type of optical modes involved in the coupling
Summary
The remarkable feature of 3D topological insulators like Bi2Se3 is the existence of metallic surface states with a Dirac-like dispersion. Theoretical studies have focused on the interaction with acoustic surface modes and gave conflicting results (0.4224, 25, 0.255, and 0.0126) The latter value seems more reasonable because the experiments[12, 13, 15, 18] indicate that modes which contribute to the electron-phonon coupling have energies between 8 and 21 meV except for the ARPES measurements[13] which revealed strong mode couplings in the Dirac cone surface states at an energy of ~3 meV. Due to a small momentum range of the Dirac cone only long wavelength acoustic phonons can participate in the EPI but their energies are very small These inconsistencies stress the need to reinvestigate the issue of electron-phonon interaction in topological surface states using ab initio calculation methods. The Dirac cone covers only a small momentum range (a few percent of the Brillouin zone) requiring rather fine grids to properly sample both electron and phonon quantities, which was overlooked in ref. 28
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