Direct Observation of One-Dimensional Peierls-type Charge Density Wave in Twin Boundaries of Monolayer MoTe₂

Abstract

One-dimensional (1D) metallic mirror-twin boundaries (MTBs) in monolayer transition metal dichalcogenides (TMDCs) exhibit a periodic charge modulation and provide an ideal platform for exploring collective electron behavior in the confined system. The underlying mechanism of the charge modulation and how the electrons travel in 1D structures remain controversial. Here, for the first time, we observed atomic-scale structures of the charge distribution within one period in MTB of monolayer MoTe2 by using scanning tunneling microscopy/spectroscopy (STM/STS). The coexisting apparent periodic lattice distortions and U-shaped energy gap clearly demonstrate a Peierls-type charge density wave (CDW). Equidistant quantized energy levels with varied periodicity are further discovered outside the CDW gap along the metallic MTB. Density functional theory (DFT) calculations are in good agreement with the gapped electronic structures and reveal they originate mainly from Mo 4d orbital. Our work presents hallmark evidence of the 1D Peierls-type CDW on the metallic MTBs and 2 offers opportunities to study the underlying physics of 1D charge modulation.

Charge Density Modulation and the Luttinger Liquid State in MoSe2 Mirror Twin Boundaries

“…For the MTBs in ML MoSe 2 , TLL was also suggested by a photoemission spectroscopy experiment, whereas a low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/S) study pointed to the Peierls-type CDW . A similar CDW has been suggested in the MTBs formed in MoTe 2 . On the other hand, Liu et al reported quantum well states (QWS) in finite length MTBs .…”

“…2 A similar CDW has been suggested in the MTBs formed in MoTe 2 . 32 On the other hand, Liu et al reported quantum well states (QWS) in finite length MTBs. 1 Jolie et al provided experimental evidence of spin-charge separation and thus the TLL in the so-called 4|4E type MTB in MoS 2 .…”

Electronic structure and signature of Tomonaga-Luttinger liquid state in epitaxial CoSb$_{1-x}$ nanoribbons

“…The CDW order could be excluded in our case as the STS data in Fig. 3c exhibit continuous suppression towards E F without any signature of CDW gap formation, in contrast to the well-defined gap structure in the STS spectra of other typical Q1D CDW systems 26,27 . On the other hand, the CDW fluctuations could cause a pseudogap opening, which may explain the spectral weight suppression 28,29 .…”

Phase control and lateral heterostructures of MoTe2 epitaxially grown on graphene/Ir(111)

“…17 As an alternative, molecular beam epitaxy (MBE) has been used to grow 2H-MoTe 2 thin films on graphene on 6H-SiC(0001), 18 SiO 2 , 19 GaAs(111)B, 20 CaF 2 , 21 InAs(111)/Si(111) 22 and c-Al 2 O 3 (0001), 23 although the small grain size of the grown layer results in poor transport properties. 23 Besides, the formation of a single MoTe 2 layer with different stoichiometry and diverse physical properties has been reported on highly oriented pyrolytic graphite (HOPG), [24][25][26] bilayer of graphene on SiC (BLG/SiC) 26,27 and MoS 2 . 28 However, the production of large domains of metallic 1T′ phase or the control of the fabrication of heterophase structures are still challenging, as a result of both the tendency of Te to desorb from the surface during the growth process and the small energy difference between the 1H and the 1T′ phases.…”