Unified Theory of Fano Resonance in the Anderson Impurity Systems

Fano Resonance in the Anderson Impurity Systems
Luo Hong-Gang
Institute of Theoretical Physics,
Chinese Academy of Sciences, 100080 Beijing
The Fano resonance [1] is a ubiquitous phenomenon observed in
many fields of physics. The characteristic feature of the Fano resonance is
its famous asymmetric lineshape as a consequence of the interference
between a discrete channel and a continuum of states.
In this talk we report a unified theory of Fano resonance in the
Anderson impurity systems. The Fano resonance has been widely
observed in the tunneling spectra measurements of 3d transition metal
atoms on the surface of noble metals, for example, Co/Au(111)[2] and
Ti/Ag(100) [3]. We proposed that the Fano resonance is due to the
interference between three channels: the Kondo resonance, the impurity
level broadening, and the continuum of states in metals. When the system
is in the Kondo regime, the channel of the impurity level broadening
plays a minor role and the Fano lineshape of Co/Au(111) can be well
fitted by the interference between the Kondo resonance and the
continuum of states in metals, as suggested by Ujsaghy et al. [4].
However, when the systems approach to or are in the mixed valence
regime, the broadened impurity level plays a key role in understanding
the experimental data, for example, Ti/Ag(100) [5].
[1] U. Fano, Phys. Rev. 124, 1866 (1961).
[2] V. Madhavan et al., Science 280, 567 (1998).
[3] K. Nagaoka et al., Phys. Rev. Lett. 88, 077205 (2002).
[4] O. Ujsaghy et al., Phys. Rev. Lett. 85, 2557 (2000).
[5] H. G. Luo et al, Phys. Rev. Lett. 92, 256602 (2004); 96, 019702(2006).
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