| The successful separation and stacking of 2D van der Waals(vdW)materials with atomic-level thickness provides a new degree of freedom for manipulating the physical properties of materials.The relatively weak interlayer vdW interaction has an important and unique position in the development of 2D vdW materials.But there are very few researches on the effect of vdW interaction in one-dimensional system that also possess an atomic scale.One of the main difficulties is to achieve atomic-level accuracy physical property measurements and manipulations in a one-dimensional system.In this thesis,we controllably prepare single nanowires and nanowire arrays by combining ultra-high vacuum molecular beam epitaxy(MBE)and scanning tunneling microscopy,and discover the modulation effects of vdW stacking on the electronic properties on the atomic scale.First,by using MBE,we achieve the controllable growth of 1D W6Te6nanowires(with the diameter of 0.8nm)on bilayer graphene/silicon carbide substrates,and determine the atomic structure of a single wires and the stacking registry of vdW-bonded nanowire arrays.Subsequently,by combining the scanning tunneling spectroscopy and first-principles calculations,we unravel the semiconductor ground state of a single nanowire with a band gap of?60me V,and an electronic structure transition from semiconductor to metal when nanowires are vdW bonded.Moreover,in metallic phase,we found that low-energy excited states behave as typical 1D correlated electronic states:Tomonaga-Luttinger liquid behaviors,and correlation strength can be tuned by the number of stacked nanowires.We observe g=0.086 for bi-wire and 0.136for six-wire,still much lower than the Fermi liquid strength of g=1.The electronic structure and correlations regulated by the stacking numbers illustrate the versatile role and potential of vdW stacking in 1D nanowire systems.Our findings also shed the light for constructions and functional manipulations of future electronic devices. |
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