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Fermi gap stabilization of an incommensurate two-dimensional superstructure
F Schiller1, J Cordón, D Vyalikh
1Donostia International Physics Center, Paseo Manuel Lardizabal 4, E-20018 Donostia-San Sebastián, Spain.
Physical Review Letters
|February 9, 2005
Summary
The Ag monolayer on Cu(111) forms a moire superstructure. A Fermi energy gap in the surface band of the incommensurate phase suggests stabilization, unlike the commensurate phase.
Area of Science:
- Surface science
- Condensed matter physics
- Materials science
Background:
- Silver (Ag) monolayers on copper (Cu(111)) substrates form moire superstructures.
- The electronic properties of these superstructures are sensitive to compression and commensurability.
Purpose of the Study:
- To investigate the electronic band structure of Ag/Cu(111) moire superstructures.
- To understand the stabilization mechanism of the incommensurate Ag/Cu(111) phase.
Main Methods:
- Analysis of surface state bands in different moire structures.
- Estimation of energy gain associated with Fermi energy gap opening.
Main Results:
- The compressed, incommensurate approximately (9.5 x 9.5) Ag/Cu(111) moire superstructure exhibits a filled surface state band with a Fermi energy gap at the Brillouin zone boundary.
- The less compressed, commensurate (9 x 9) moire of two Ag layers shows a gapless surface band.
- The estimated energy gain from gap opening is comparable to the elastic energy change for structural modification.
Conclusions:
- The Fermi energy gap in the incommensurate phase likely stabilizes this structure.
- The findings suggest the potential for a charge density wave state in the Ag/Cu(111) system.