Quantum well states as Fabry-Pérot modes in Mg/W(110)
Chulkov, Eugene; Leonardo, Aritz; Schiller, Frederik; Ortega, Jose Enrique
Spain

Electron confinement within a film results in discrete quantum-well states observable by angle resolved photoemission. These spectra can be analyzed in the same way as an optical Fabry-Pérot interferometer filled with a medium.
In the case of a quantum well, the initial state undergoes multiple reflections between the two boundaries, and becomes modulated by a interference factor:
1/(1-Rexp i(2kNt+Φ)exp(-Nt/λ))
Recent ARPES measurements performed by Schiller et al. have shown that the linewidths of QW states in Mg(0001) increase as the Fermi level is approached. This fact is in clear contradiction with the general behavior for Fermi liquids, where linewidths obey a quadratic form which is proportional to ~­(E-EF)2 .
We show that the flux of electrons escaping through the interface towards the substrate plays a crucial role in this system and is responsible for the anomalous broadening of the linewidths.
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