Angle resolved photoemission spectroscopy reveals spin charge separation in metallic MoSe2 grain boundary

Abstract

Material line defects are one-dimensional structures but the search and proof of electron behaviour consistent with the reduced dimension of such defects has been so far unsuccessful. Here we show using angle resolved photoemission spectroscopy that twin-grain boundaries in the layered semiconductor MoSe2 exhibit parabolic metallic bands. The one-dimensional nature is evident from a charge density wave transition, whose periodicity is given by kF/π, consistent with scanning tunnelling microscopy and angle resolved photoemission measurements. Most importantly, we provide evidence for spin- and charge-separation, the hallmark of one-dimensional quantum liquids. Our studies show that the spectral line splits into distinctive spinon and holon excitations whose dispersions exactly follow the energy-momentum dependence calculated by a Hubbard model with suitable finite-range interactions. Our results also imply that quantum wires and junctions can be isolated in line defects of other transition metal dichalcogenides, which may enable quantum transport measurements and devices.

Tomonaga-Luttinger Liquid in a Box: Electrons Confined within MoS2 Mirror-Twin Boundaries

“…Their structures were unambiguously determined by transmission electron microscopy [21][22][23], and density functional theory invariably predicted the MTBs to host one-dimensional, metallic states [24][25][26][27] that are protected through the large band gap of approximately 2 eV in the surrounding 2D-layer. Intense research yielded partly conflicting results regarding the electronic structure of a specific MTB in a monolayer of MoSe 2 resting on a van der Waals substrate [19,28,29], namely the 4|4P MTB consisting of 4-fold rings sharing a point at the chalcogene site [24,30]. By using room temperature as well as low-temperature (4K) STM and STS, Liu et al [28] found a quantum well state emerging from the finite length of the interpenetrating MTBs.…”

Role of a higher-dimensional interaction in stabilizing charge density waves in quasi-one-dimensional NbSe3 revealed by angle-resolved photoemission spectroscopy

“…Dimensional considerations have also been highlighted in the CDW mechanism of NbSe 2 [10][11][12]. Given the current inter-est in producing heterostructures of 2D-transition metal dichalcogenides, as well as the possibility of investigating quasi-1D edge effects in such materials [13], the relevance of mixed dimensionality systems with weak coupling between chains or layers is clear. Here we investigate NbSe 3 , a paradigmatic quasi-1D CDW material, in order to investigate the influence of a higher-dimensional environment on charge ordering within a reduced-dimensional system.…”

Engineering the Electronic Properties of Two‐Dimensional Transition Metal Dichalcogenides by Introducing Mirror Twin Boundaries

“…[30,33] These are promising for studying onedimensional electron dynamics, such as charge density waves [34] and Tomonaga-Luttinger liquid. [35] The variety of means to produce these MTBs coupled with the existence of different types of MTBs suggests that unprecedented control over the type and density of MTB grain boundaries, and consequently of their properties, could be achieved.…”

“…Such systems are promising for studying one-dimensional electron dynamics, such as charge density waves and TomonagaLuttinger liquid. [34,35] Finally, when more than one layer is considered, the inversion domain formation in only one layer also leads to unusual stacking between the layers. In particular, while bilayer TMDs obtained from the 2H polymorph possess inversion symmetry, the region with inversion domain in one layer does not.…”