open access

https://hdl.handle.net/2115/67147

Direct observation of mono-layer, bi-layer, and tri-layer charge density waves in 1T-TaS2 by transmission electron microscopy without a substrate

英語

2017-04-25

Nature Publishing Group

npj Quantum Materials

2

1-6

Charge-density-waves, which occur mainly in low-dimensional systems, have a macroscopic wave function similar to superfluids and superconductors. Kosterlitz-Thouless transition is observed in superfluids and superconductors, but the presence of Kosterlitz-Thouless transition in ultra-thin charge-density-waves systems has been an open problem. We report the direct real-space observation of charge-density-waves with new order states in mono-layer, bi-layer, and tri-layer 1T-TaS2 crystals using a low voltage scanning-transmission-electron-microscopy without a substrate. This method is ideal to observe local atomic structures and possible defects. We clearly observed that the mono-layer crystal has a new triclinic stripe charge-density-waves order without satisfying the triple q condition q(1) + q(2) + q(3) = 0. A strong electron-phonon interaction gives rise to new crevasse (line) type defects instead of disclination (point) type defects due to the Kosterlitz-Thouless transition. These results reaffirm the importance of the electron-phonon interaction in mono-layer nanophysics.

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2397-4648