Infrared nanoimaging of the metal-insulator transition in the charge-density-wave van der Waals material 1T-TaS2

Alex J. Frenzel, Alexander S. McLeod, Dennis Zi Ren Wang, Yu Liu, Wenjian Lu, Guangxin Ni, Adam W. Tsen, Yuping Sun, Abhay N. Pasupathy, D. N. Basov

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Using scanning near-field optical microscopy at cryogenic temperatures, we explored the first-order metal-insulator transition of exfoliated 1T-TaS2 microcrystals on a SiO2/Si substrate. We clearly observed spatially separated metallic and insulating states during the transition between commensurate and nearly commensurate charge-density-wave phases. The capability to probe electrodynamics on nanometer length scales revealed temperature-dependent electronic properties of the insulating and metallic regions near the transition temperature. At fixed temperature, a remarkably broad spatial boundary between insulating and metallic regions was observed, across which the nano-optical signal smoothly evolved over a length scale of several hundred nanometers. To understand these observations, we performed Ginzburg-Landau calculations to determine the charge-density-wave structure of the domain boundary, which revealed the existence of an intermediate electronic phase with unique properties distinct from the bulk thermodynamic phases.

Original languageEnglish (US)
Article number035111
JournalPhysical Review B
Issue number3
StatePublished - Jan 8 2018
Externally publishedYes

Bibliographical note

Funding Information:
We acknowledge helpful discussions with K. W. Post and A. Charnukha. This research was supported through DOE-BES Grant No. DE-FG02-00ER45799. D.N.B. is the Moore Foundation Investigator in quantum materials GBMF4533. Sample fabrication at Columbia University was supported by the AFOSR (Grant No. FA9550-16-1-0601, A.N.P.) and from shared facilities supported by the NSF MRSEC (Grant No. DMR-1420634). D.Z.-R.W. acknowledges support from NSF IGERT (Grant No. DGE-1069240). Y.L., W.L., and Y.S. acknowledge support from the National Key Research and Development Program under Contract No. 2016YFA0300404, the National Nature Science Foundation of China under Contracts No. 11674326 and No. U1232139.

Publisher Copyright:
© 2018 American Physical Society.


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