While parallel segments in the Fermi level contours, often found at the surfaces of topological insulators (TIs) would imply "strong" nesting conditions, the existence of charge density waves (CDWs) - periodic modulations of the electron density - has not been verified up to now. Here, we report the observation of a CDW at the surface of the Bi2Te2Se(111), below ≈350K by helium atom scattering, and thus experimental evidence of a CDW involving Dirac topological electrons. Deviations of the order parameter observed below 180K and a low temperature break of time reversal symmetry suggest the onset of a spin density wave with the same period as the CDW in presence of a prominent electron-phonon interaction originating from the Rashba spin-orbit coupling.
@article{arxiv.2111.02323,
title = {Observation of Dirac Charge Density Waves in Bi$_2$Te$_2$Se},
author = {Adrian Ruckhofer and Giorgio Benedek and Martin Bremholm and Wolfgang E. Ernst and Anton Tamtögl},
journal= {arXiv preprint arXiv:2111.02323},
year = {2023}
}