Abstract
In one-dimensional (1D) metallic systems, the diverging electron susceptibility and electron-phonon coupling collaboratively drive the electrons into a charge density wave (CDW) state. However, strictly 1D system is unstable against perturbations, whose effect on CDW order requires clarification ideally with altered coupling to surroundings. Here, we fabricate such a system with nanowires of Mo6Se6 bundles, which are either attached to edges of monolayer MoSe2 or isolated freely, by post-annealing the preformed MoSe2. Using scanning tunneling microscopy (STM), we visualized charge modulations and CDW gaps with prominent coherent peaks in the edge-attached nanowires. Astonishingly, the CDW order becomes suppressed in the isolated nanowires, showing CDW correlation gaps without coherent peaks. The contrasting behavior, as revealed with theoretical modeling, is interpreted as the effect of phason-polarons on the 1D CDW state. Our work elucidates a possibly unprecedented many body effect that may be generic to strictly 1D system but undermined in quasi-1D system.
Highlights
When electrons are confined in an atomic chain, correlations among them get enhanced, causing instability of the Fermi surface due to its perfect nesting and reduced screening [1]
In one-dimensional (1D) metallic systems, the diverging electron susceptibility and electron-phonon coupling collaboratively drive the electrons into a charge density wave (CDW) state
Its atomic resolution image is reproduced by our simulated STM image with density functional theory (DFT) based on the crystal structure of a four-wire Mo6Se6 bundle [Fig. 1(b) and Supplemental Note 1 [28] ]
Summary
When electrons are confined in an atomic chain, correlations among them get enhanced, causing instability of the Fermi surface due to its perfect nesting and reduced screening [1] This instability makes the systems susceptible to electron-electron and electron-phonon interactions, driving them into a rich variety of exotic correlated quantum states that are distinguished from 3D, such as the Tomonaga-Luttinger liquid, spin density waves, and charge density waves (CDWs). Recent experiments report CDW orders in single silicide nanowires [12] and a mirror twin boundary of monolayer MoSe2 [13] that are electronically isolated 1D systems, they are still coupled to the lattice of supporting surroundings, whose phonons are essentially 2D. Both conditions promise a system ideal for the study of purely 1D CDW order
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