Atomic lattice disorder in charge-density-wave phases of exfoliated dichalcogenides (1T-TaS2).
Charge-density waves (CDWs) and their concomitant periodic lattice distortions (PLDs) govern the electronic properties in several layered transition-metal dichalcogenides. In particular, 1T-TaS2undergoes a metal-to-insulator phase transition as the PLD becomes commensurate with the crystal lattice. Here we directly image PLDs of the nearly commensurate (NC) and commensurate (C) phases in thin, exfoliated 1T-TaS2using atomic resolution scanning transmission electron microscopy at room and cryogenic temperature. At low temperatures, we observe commensurate PLD superstructures, suggesting ordering of the CDWs both in- and out-of-plane. In addition, we discover stacking transitions in the atomic lattice that occur via one-bond-length shifts. Interestingly, the NC PLDs exist inside both the stacking domains and their boundaries. Transitions in stacking order are expected to create fractional shifts in the CDW between layers and may be another route to manipulate electronic phases in layered dichalcogenides.
School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853.
Robert
R
Hovden
Department of Physics, Columbia University, New York, NY 10027; Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada; Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
Adam W
AW
Tsen
School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853.
Pengzi
P
Liu
Department of Physics, Cornell University, Ithaca, NY 14853.
Benjamin H
BH
Savitzky
Department of Physics, Cornell University, Ithaca, NY 14853.
Ismail
I
El Baggari
Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China.
Yu
Y
Liu
Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China.
Wenjian
W
Lu
Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China; High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, People's Republic of China; Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing 210093, People's Republic of China.
Yuping
Y
Sun
Department of Physics, Harvard University, Cambridge, MA 02138.
Philip
P
Kim
Department of Physics, Columbia University, New York, NY 10027.
Abhay N
AN
Pasupathy
School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853; Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY 14853 lena.f.kourkoutis@cornell.edu.
Lena F
LF
Kourkoutis
2D materials; STEM; TaS2; charge-density wave; electron microscopy
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