Experimental signature of layer skyrmions and implications for band topology in twisted WSe2 bilayers

TL;DR

This study provides experimental evidence of layer skyrmion textures in twisted WSe2 bilayers, linking moiré potential variations to topological band features through scanning tunneling spectroscopy.

Contribution

First experimental observation of layer skyrmion textures in twisted WSe2 bilayers, connecting real-space LDOS profiles to moiré band topology.

Findings

Gamma-valley states experience a ~120 meV moiré potential.

K-valley states are affected by a ~30 meV moiré potential.

Opposite layer polarizations at MX and XM sites confirm layer skyrmion textures.

Abstract

Transition metal dichalcogenide (TMD) twisted homobilayers have been established as an ideal platform for studying strong correlation phenomena, as exemplified by the recent discovery of fractional Chern insulator (FCI) states in twisted MoTe2 and Chern insulators (CI) and unconventional superconductivity in twisted WSe2 (tWSe2). In these systems, nontrivial topology in the strongly layer-hybridized regime can arise from a spatial patterning of interlayer tunneling amplitudes and layer-dependent potentials that yields a lattice of layer skyrmions. Here we report on experimental signatures of skyrmion textures in the layer degree of freedom of Rhombohedral-stacked (R-stacked) tWSe2 homobilayers. This observation is based on scanning tunneling spectroscopy that separately resolves the Gamma-valley and K-valley moir\'e electronic states. We show that Gamma-valley states are subjected to a moir\'e potential with an amplitude of ~ 120 meV. At ~150 meV above the Gamma-valley, the K-valley states are subjected to a weaker moir\'e potential of ~30 meV. Most significantly, we reveal opposite layer polarizations of the K-valley at the MX and XM sites within the moir\'e unit cell, confirming the theoretically predicted layer skyrmion texture. The dI/dV mappings allow the parameters that enter the continuum model of moir\'e bands in twisted TMD bilayers to be determined experimentally, further establishing a direct correlation between the shape of the LDOS profile in real space and the topology of topmost moir\'e band.