Fig. 1: Phase diagram of 2.7-degree twisted WSe2 bilayers.
From: Correlated states controlled by a tunable van Hove singularity in moiré WSe2 bilayers
a Left: schematic of a dual-gated twisted WSe2 bilayer device with a WS2 monolayer sensor. Few-layer graphite is used as the gate electrodes, and hexagonal boron nitride (hBN), the gate dielectrics and spacer between the sample and sensor. Top and bottom gate voltages (Vtg and Vbg) control the moiré lattice filling factor \(\nu\) and the out-of-plane electric field \(E\). Right: honeycomb moiré lattice with sublattices at the MX (orange) and XM (blue) sites (\({{\rm{M}}}={{\rm{W}}}\), black circles; \({{\rm{X}}}={{\rm{Se}}}\), grey circles). b Left: continuum model band structure with the first two moiré valence bands of the K-valley state along the directions of \(\gamma -\kappa -m-\gamma\) in the moiré Brillouin zone (E = 0). Right: density of states (DOS) showing van Hove singularities (vHS). c, d Spectrally integrated reflection contrast (RC) of the sample intralayer exciton (c) and the sensor 2 s exciton (d) as a function of filling factor \(\nu\) and electric field \(E\) at 1.6 K. The dashed lines extracted from (c) (see main text) separate the layer-hybridized region for low fields from the layer-polarized region for high fields. Black arrows mark the correlated insulators at fractional filling factors.
