Imaging gate-tunable Tomonaga-Luttinger liquids in 1H-MoSe2 mirror twin boundaries

The authors use scanning tunnelling microscopy and spectroscopy to visualize the electronic structure of mirror twin boundaries, revealing a Tomonaga-Luttinger liquid. One-dimensional electron systems exhibit fundamentally different properties than higher-dimensional systems. For example, electron-electron interactions in one-dimensional electron systems have been predicted to induce Tomonaga-Luttinger liquid behaviour. Naturally occurring grain boundaries in single-layer transition metal dichalcogenides exhibit one-dimensional conducting channels that have been proposed to host Tomonaga-Luttinger liquids, but charge density wave physics has also been suggested to explain their behaviour. Clear identification of the electronic ground state of this system has been hampered by an inability to electrostatically gate such boundaries and tune their charge carrier concentration. Here we present a scanning tunnelling microscopy and spectroscopy study of gate-tunable mirror twin boundaries in single-layer 1H-MoSe2 devices. Gating enables scanning tunnelling microscopy and spectroscopy for different mirror twin boundary electron densities, thus allowing precise characterization of electron-electron interaction effects. Visualization of the resulting mirror twin boundary electronic structure allows unambiguous identification of collective density wave excitations having two velocities, in quantitative agreement with the spin-charge separation predicted by finite-length Tomonaga-Luttinger liquid theory.

Automated summary

The authors used scanning tunnelling microscopy and spectroscopy to study the mirror twin boundaries in single-layer 1H-MoSe2 devices. By adjusting the electron density, they successfully visualized the electronic structure of the mirror twin boundaries and confirmed the presence of density wave excitations and spin-charge separation effects, in agreement with the predictions of the Tomonaga-Luttinger liquid theory.