Arkady M. Satanin

Classical analogy of Fano resonances

We present an analogy of Fano resonances in quantum interference to classical resonances in the harmonic oscillator system. It has a manifestation as a coupled behaviour of two effective oscillators associated with propagating and evanescent waves. We illustrate this point by considering a classical system of two coupled oscillators and interfering electron waves in a quasi-one-dimensional narrow constriction with a quantum dot. Our approach provides a novel insight into Fano resonance physics and provides a helpful view in teaching Fano resonances.

Characteristics of transmission resonance in a quantum-dot superlattice

We investigate phase-coherent electron transport through height-varying potential barriers in a quantum-dot superlattice. Due to the aspect ratio variations of two alternating potential heights in the quantum channel, well-arranged resonant peaks in the first miniband of each plateau are divided into the paired peaks of two groups, which produce an extra gap inside each miniband. In addition, for a five barrier case, the second and third resonant peaks in the miniband are no longer distinguishable at a critical aspect ratio, and the amplitude of this degenerate peak becomes smaller than one and eventually approaches zero. The mean lifetimes of the resonant peaks whose amplitudes remain unity are studied. We also examine the resonant tunneling with under-unity transmission in the one-dimensional superlattice system with alternating potential barriers. Finally, it is found that the “quasi-resonance” appears in a quantum-dot superlattice with 13 barriers consisting of 2 alternating potential heights.

Collapse of resonance in quasi-one-dimensional quantum channels

We study the resonance structure of the conductance (transmissivity) of a quasi-one-dimensional channel that contains an attractive impurity of finite dimensions and derive an exact expression for the scattering matrix. We show that an impurity of finite dimensions may cause a set of Fano resonances to appear in the transmissivity. We also find that due to the coherent interaction the Fano resonances can collapse and discrete levels may appear in the continuum. Finally, we establish the wave function of the discrete levels and study the channel transmissivity in the critical regime.

Resonance characteristics through double quantum dots embedded in series in an Aharonov-Bohm ring

Stimulated by recent intriguing experiments with a quantum dot in an Aharonov–Bohm (AB) ring, we investigate novel resonant phenomena by studying the total transmission probability of nanoscale AB rings with embedded double quantum dots in one arm and a magnetic flux passing through its centre. In this system, we show the overlapping and merging of both Breit-Wiger (BW) and Fano resonances as the interaction parameter between the dots changes. In the strong overlapping regime of Fano resonances, the transmission zeros leave the real-energy axis and move away in opposite directions in the complex-energy plane. The simultaneous swings (from Fano to BW and then back to Fano resonance) of a pair of Fano resonances in the overlapping regime are observed by modulating the magnetic flux threading the AB ring. The periodic tuning of the Fano resonance for a fixed interaction parameter is also discussed as the magnetic flux increases.

Optical properties of quantum dots produced from inverted-gap semiconductors

We investigate the electron spectrum and optical response of quantum dots (QDs) produced from narrow-band semiconductors with the inverted band structure (the negative sign of the energy gap). It is shown that in addition to usual size-quantized states which are located above the gap edge in normal band materials, there exist states residing inside the gap (analogous of the Tamm states) in inverted band structures. Such states manifest themselves in the far infrared part of emission and absorption spectra, measurement of which allows us to extract information about the QD surface.

How a Fano Resonance Crosses the Mobility Edge in Quantum Waveguides

Abstractnew scenario for the occurrence of a Fano resonance in the transmission probability of electron waveguides is investigated using a coupled-channel theory. Both a quantum dot and an antidot with either short- or finite-range interaction are embedded in the electron waveguide. Particularly, when the Fano resonance occurs close to the mobility edge (channel threshold), it is shown that Γ~U124/3, where Γ is the resonance width and U12 is the coupling strength between bound state and continuum. This is in contrast to the usual result Γ ~U122, which is valid when the resonance occurs far from the mobility edge. Furthermore, it is shown that increasing the size of both dot and antidot leads to larger resonance width.

Collision of Fano Resonances in a Molecular Ring

We examine new effects arising from the collision of Fano dipole resonances as affecting the transmission through an Aharonov-Bohm (AB) ring. The behavior of the zeros of the transmission amplitude as a function of magnetic field is investigated for various coupling integrals between quantum dots in the ring. It is shown that the collision of two Fano-dipoles forms a new quasi-particle, which behaves as a coupled object called a Fano-quadrupole.

Size Dependence Of The Optical Gap In Silicon Nanocrystals Embedded Into a‐Si:H Matrix

A simple model for Si nano‐crystallites (NC’s) embedded in amorphous silicon matrix is considered within the envelope function approximation. It is shown that, although the effect of the NC’s on the tail states is small, there are electron and hole states localized in the NC’s and separated by an energy of the order of 2eV. These states can be responsible for the experimentally observed features in the photoluminescence spectra of NC‐Si/a‐Si:H films.