DOI: 10.1209/epl/i2002-00589-8


Europhys. Lett., 57 (6) , pp. 859-865 (2002)

Observation of a quasi-1D Mott-Hubbard insulator: The re-entrant - surface

J. R. Ahn¹, N. D. Kim¹, S. S. Lee¹, K. D. Lee¹, B. D. Yu², D. Jeon³, K. Kong⁴ and J. W. Chung<sup>1

1</sup>  Physics Department and Basic Science Research Institute, Pohang University of Science and Technology - San 31 Hyoja Dong, Pohang 790-784, Korea
²  Department of Physics, University of Seoul - 90 Cheonnong-dong Tongdaemun-gu, Seoul 130-743, Korea
³  Department of Physics, Myong Ji University - Yongin Kyunggi-Do Seoul 449-728, Korea
⁴  IQUIPS, University of Seoul - 90 Cheonnong-dong, Tongdaemun-gu Seoul 130-743, Korea

(Received 13 August 2001; accepted 19 December 2001)

Abstract
We have investigated the origin of a semiconducting phase of the re-entrant - surface formed by adding extra adatoms on the earlier phase at 1/3 monolayers (MLs). The additional adatoms are found to form quasi-one-dimensional (1D) atomic chains in our scanning tunnelling microscopy images while keeping the surface semiconducting. The unique features in our valence band and in high-resolution electron-energy-loss spectra suggest that the re-entrant surface is a Mott-Hubbard-type insulator. We thus report a novel quasi-1D insulator-insulator transition where electron-electron correlation plays a decisive role.

PACS
71.30.+h - Metal-insulator transitions and other electronic transitions.
73.20.-r - Electron states at surfaces and interfaces.
61.18.-j - Other methods of structure determination.


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