Figure 25.

Luttinger liquid behavior in ${\text{tWTe}}_2$ moiré system. (a) The crystal structure for monolayer ${\text{WTe}}_2$. The W atoms are sandwiched by two Te atom layers. From the top view, the W atoms (blue) form zigzag chains. The dashed square denotes the unit cell. (b) Moiré superlattice of ${\text{tWTe}}_2$, where only the W atoms are shown. The alternating AA and AB 1D stripes are illustrated. (c) conductive AFM image of a ${\text{tWTe}}_2$ sample. (d) Optical image of a typical device, with the contact regions marked with red solid lines and the two layers of ${\text{WTe}}_2$ with yellow and white dashed lines, respectively. (e) Cartoon illustration of the device structure. From bottom to top: bottom graphite, bottom hBN, electrodes, thin hBN, ${\text{tWTe}}_2$, top hBN, and top graphite. (f) Measurement configuration for the hard and easy directions. The squares denote the contacts, and the gray lines indicate the moiré stripes. s, source; d, drain. (g) Four-probe resistance of the hard and easy direction shown in panel (f), measured at 1.8 K, as a function of the gate-induced doping density $n_{\text{g}}$ of the device. (h) The anisotropy ratio, $R_{\text{hard}}/R_{\text{easy}}$ with $R_{\text{hard}}$ and $R_{\text{easy}}$ in g, versus $n_{\text{g}}$. (i) The across-wire differential conductance $\text{d}I/\text{d}V$ measured under different d.c. bias and temperature, with the doping fixed on the hole side. (j) Scaled differential conductance $(\text{d}I/\text{d}V)/T^{\text{a}}$, plot against $\text{eV}/k_{\text{B}}T$ (same data in panel (i)), showing that all the data collapse into one curve. Adapted with permission from ref 453. Copyright 2022 Springer Nature.