Theory of possible sliding regimes in twisted bilayer WTe_2

Inspired by the observation of increasingly one-dimensional (1D) behavior with decreasing temperature in small-angle twisted bilayers of WTe_2 (tWTe_2), we theoretically explore the exotic sliding regimes that could be realized in tWTe_2. At zero displacement field, while hole-doped tWTe_2 can be thought of as an array of weakly coupled conventional two-flavor 1D electron gases (1DEGs), the electron-doped regime is equivalent to coupled four-flavor 1DEGs , due to the presence of an additional "valley” degree of freedom. In the decoupled limit, the electron-doped system can thus realize phases with a range of interesting ordering tendencies, including 4k_F charge-density-wave and charge-4e superconductivity. Dimensional crossovers and cross-wire transport due to inter-wire couplings of various kinds are also discussed. We find that a sliding Luther-Emery liquid with small inter-wire couplings is probably most consistent with current experiments on hole-doped tWTe_2.