Resonant Tunneling in an Aharonov-Bohm Ring with a Quantum Dot (original) (raw)

Resonant tunneling through a quantum dot in an Aharanov-Bohm ring: Results from bosonization

Physical Review B, 2000

We study coherent charge tunneling through a one-dimensional interacting ring with a one-dimensional quantum dot embedded in one of its arms through bosonisation. The symmetries of the effective action explain many of the features such as phase change between resonances, in-phase successive resonances and phase-locking, which have been observed in experiments of coherent transport in mesoscopic rings, with a quantum dot. We also predict changes in the behaviour of the tunneling conductance in the presence of an Aharanov-Bohm flux through the ring. We argue that these results hold true in general for any dot.

Results from bosonisation for resonant tunneling through a quantum dot in an Aharanov-Bohm ring

arXiv (Cornell University), 1999

Resonance and phase shift in an open Aharonov–Bohm ring with an embedded quantum dot

Journal of Physics: Condensed Matter, 2009

The transmission and phase properties of electron transport through a quantum dot (QD) with variable coupling to a third-terminal probe are investigated analytically for the case of the QD connected directly to source and drain reservoirs and when the QD is embedded in one arm of an Aharonov-Bohm (AB) ring. Using the tight-binding model, explicit analytical expressions of the transmission through the QD for each case are given. Expressions for the conductance with coupling to the third terminal, which breaks unitarity and phase-locking, are also given. It is shown that in a three-terminal interferometer the zero of the Fano resonance in the transmission moves off the real energy axis for finite values of the coupling parameter. The zero orbits around the pole in the complex energy plane as a function of magnetic flux through the ring, and can be returned to the real energy axis unless the coupling parameter exceeds a critical value. With the QD embedded in one arm of the AB ring, the electron transmission and the transmission phase, and the phase of the AB oscillations, are described in relation to the degree of coupling to the third-terminal probe which opens the interferometer. By tuning the degree of coupling to the probe, it is shown that the phase of the AB oscillations can be made to match the intrinsic phase of the QD, facilitating experimental characterization of the phase response of the QD.

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

Journal of Physics D: Applied Physics, 2006

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.

Transmission through a quantum dot molecule embedded in an Aharonov-Bohm interferometer

Journal of Physics: …, 2011

We study theoretically the transmission through a quantum dot molecule embedded in the arms of an Aharonov-Bohm four quantum dot ring threaded by a magnetic flux. The tunable molecular coupling provides a transmission pathway between the interferometer arms in addition to those along the arms. From a decomposition of the transmission in terms of contributions from paths, we show that antiresonances in the transmission arise from the interference of the self-energy along different paths and that application of a magnetic flux can produce the suppression of such antiresonances. The occurrence of a period of twice the quantum of flux arises to the opening of transmission pathway through the dot molecule. Two different connections of the device to the leads are considered and their spectra of conductance are compared as a function of the tunable parameters of the model.

Conductance phases in the quantum dots of an Aharonov-Bohm ring

Physical Review B, 2006

The regimes of growing phases (for electron numbers N ≈ 0−8) that pass into regions of self-returning phases (for N > 8), found recently in quantum dot conductances by the Weizmann group are accounted for by an elementary Green function formalism, appropriate to an equispaced ladder structure (with at least three rungs) of electronic levels in the quantum dot. The key features of the theory are physically a dissipation rate that increases linearly with the level number (and tentatively linked to coupling to longitudinal optical phonons) and a set of Fano-like meta-stable levels, which disturb the unitarity, and mathematically the change over of the position of the complex transmission amplitude-zeros from the upper-half in the complex gap-voltage plane to the lower half of that plane. The two regimes are identified with (respectively) the Blaschke-term and the Kramers-Kronig integral term in the theory of complex variables.

Mesoscopic Fano effect in a quantum dot embedded in an Aharonov-Bohm ring

Physical Review B, 2003

The Fano effect, which occurs through the quantum-mechanical cooperation between resonance and interference, can be observed in electron transport through a hybrid system of a quantum dot and an Aharonov-Bohm ring. While a clear correlation appears between the height of the Coulomb peak and the real asymmetric parameter q for the corresponding Fano line shape, we need to introduce a complex q to describe the variation of the line shape by the magnetic and electrostatic fields. The present analysis demonstrates that the Fano effect with complex asymmetric parameters provides a good probe to detect a quantum-mechanical phase of traversing electrons.

Quantum interference effects in two double quantum dots-molecules embedded in an Aharonov–Bohm ring

Physica E: Low-dimensional Systems and Nanostructures, 2010

We study equilibrium and non-equilibrium transport of non-interacting electrons through two quantum dot molecules embedded in an Aharonov-Bohm interferometer, and focus in several quantum interference effects occurring in both regimes. We obtain analytical expressions for the transmission and the density of states, and we calculate numerically the current at zero temperature. We show that the system exhibits Fano resonances, total suppression of transmission, and bound states in the continuum. In equilibrium we find a magnetic flux-dependent effective level attraction and lines of perfect transmission when the intramolecular coupling is weak. This feature has strong consequences in the non-equilibrium regime, where the I-V characteristics displays a region of negative differential conductance induced by the magnetic flux. The current suffers an abrupt rise for small bias voltages as consequence of an effective level attraction of the hybridized levels produced by the flux. The decrease of current is result of the destruction of this effect when the bias is increased.