Charge Density Wave Vortex Lattice Observed in Graphene-Passivated 1T-TaS<sub>2</sub> by Ambient Scanning Tunneling Microscopy.

Altvater, Michael A; Tilak, Nikhil; Rao, Skandaprasad; Li, Guohong; Won, Choong-Jae; Cheong, Sang-Wook; Andrei, Eva Y · Nano Lett · 2021

basic_science · Level V

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Abstract

The nearly commensurate charge density wave (CDW) excitations native to the transition-metal dichalcogenide crystal, 1T-TaS<sub>2</sub>, under ambient conditions are revealed by scanning tunneling microscopy (STM) and spectroscopy (STS) measurements of a graphene/TaS<sub>2</sub> heterostructure. Surface potential measurements show that the graphene passivation layer prevents oxidation of the air-sensitive 1T-TaS<sub>2</sub> surface. The graphene protective layer does not however interfere with probing the native electronic properties of 1T-TaS<sub>2</sub> by STM/STS, which revealed that nearly commensurate CDW hosts an array of vortex-like topological defects. We find that these topological defects organize themselves to form a lattice with quasi-long-range order, analogous to the vortex Bragg glass in type-II superconductors but accessible in ambient conditions.