Surface transport anomalies of quasi-one-dimensional weak topological insulators

Prototypical weak topological insulators (WTI) have been theoretically predicted to be realized in quasi-one-dimensional materials Bi4X4 (X = Br, I) [PRL 116, 066801 (2016)] and then experimentally confirmed via ARPES [PRX 11, 031042 (2021) & Nature 566, 518 (2019)]. The unique surface states of such a WTI have two entangled Dirac cones with strong anisotropy. We study theoretically the integer quantum Hall effect of such WTI surface states and show the important roles played by the special geometry, symmetry, topology, and their interplay in Bi4X4. We also predict prominent signatures in transport experiments.