Quantum Hall Effect in Quasi-One-Dimensional Weak Topological Insulator*

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 in ARPES [Nature (London) 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.