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Mottness versus unit-cell doubling as the driver of the insulating state in 1T-TaS2.

ABSTRACT: If a material with an odd number of electrons per unit-cell is insulating, Mott localisation may be invoked as an explanation. This is widely accepted for the layered compound 1T-TaS2, which has a low-temperature insulating phase comprising charge order clusters with 13 unpaired orbitals each. But if the stacking of layers doubles the unit-cell to include an even number of orbitals, the nature of the insulating state is ambiguous. Here, scanning tunnelling microscopy reveals two distinct terminations of the charge order in 1T-TaS2, the sign of such a double-layer stacking pattern. However, spectroscopy at both terminations allows us to disentangle unit-cell doubling effects and determine that Mott localisation alone can drive gap formation. We also observe the collapse of Mottness at an extrinsically re-stacked termination, demonstrating that the microscopic mechanism of insulator-metal transitions lies in degrees of freedom of inter-layer stacking.

SUBMITTER: Butler CJ

PROVIDER: S-EPMC7235044 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Mottness versus unit-cell doubling as the driver of the insulating state in 1T-TaS<sub>2</sub>.

Butler C J CJ Yoshida M M Hanaguri T T Iwasa Y Y

Nature communications 20200518 1

If a material with an odd number of electrons per unit-cell is insulating, Mott localisation may be invoked as an explanation. This is widely accepted for the layered compound 1T-TaS<sub>2</sub>, which has a low-temperature insulating phase comprising charge order clusters with 13 unpaired orbitals each. But if the stacking of layers doubles the unit-cell to include an even number of orbitals, the nature of the insulating state is ambiguous. Here, scanning tunnelling microscopy reveals two disti ...[more]

PMID: 32424136

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