The commensurate charge-density-wave phase of the prototypical transition metal dichalcogenide 1T-TaS2 is investigated by temperature- and polarization-dependent infrared spectroscopy, revealing distinct charge dynamics parallel and perpendicular to the layers. Supported by density-functional-theory calculations, we show that the in-plane electronic structure in the low-temperature commensurate phase is reconstructed by the 13×13 distortion of the Ta layers. In contrast, the out-of-plane response is governed by a quasi-one-dimensional, Peierls-like dimerization of the two-dimensional star-of-David layers. Our results identify this dimerization as the dominant mechanism of the metal-to-insulator transition in both directions, ruling out a significant role of electronic correlations.
@article{arxiv.2512.23883,
title = {Unconventional anisotropic charge dynamics in bulk $1T$-TaS$_2$ induced by interlayer dimerization},
author = {Achyut Tiwari and Maxim Wenzel and Renjith Mathew Roy and Christian Prange and Bruno Gompf and Martin Dressel},
journal= {arXiv preprint arXiv:2512.23883},
year = {2026}
}