Quantum interference effects in multi-channel correlated tunneling structures

In multi-channel tunneling systems quantum interference effects modify tunneling conductance spectra due to Fano effect. We investigated the impact of Hubbard type Coulomb interaction on tunneling conductance spectra for the system formed by several interacting impurity atoms or quantum dots localised between the contact leads. It was shown that the Fano shape of tunneling conductance spectra strongly changes in the presence of on-site Coulomb interaction between localised electrons in the intermediate system. The main effect which determines the shape of the tunneling peaks could be not Fano interference but mostly nonequilibrium dependence of the occupation numbers on bias voltage.

Transition to strong coupling regime in hybrid plasmonic systems: exciton-induced transparency and Fano interference

We present a microscopic model describing the transition to a strong coupling regime for an emitter resonantly coupled to a surface plasmon in a metal–dielectric structure. We demonstrate that the shape of scattering spectra is determined by an interplay of two distinct mechanisms. First is the near-field coupling between the emitter and the plasmon mode which underpins energy exchange between the system components and gives rise to exciton-induced transparency minimum in scattering spectra prior to the transition to a strong coupling regime. The second mechanism is the Fano interference between the plasmon dipole and the plasmon-induced emitter’s dipole as the system interacts with the radiation field. We show that the Fano interference can strongly affect the overall shape of scattering spectra, leading to the inversion of spectral asymmetry that was recently reported in the experiment.

Connecting Fano interference and the Jaynes-Cummings model in cavity magnonics

We show that Fano interference can be realized in a macroscopic microwave cavity coupled to a spin ensemble at room temperature. Via a formalism developed from the linearized Jaynes-Cummings model of cavity electromagnonics, we show that generalized Fano interference emerges from the photon–magnon interaction at low cooperativity. In this regime, the reflectivity approximates the scattering cross-section derived from the Fano-Anderson model. Although asymmetric lineshapes in this system are often associated with the Fano formalism, we show that whilst Fano interference is actually present, an exact Fano form cannot be achieved from the linear Jaynes-Cummings model. In the Fano model an additional contribution arises, which is attributed to decoherence in other systems, and in this case is due to the resonant nature of the photonic mode. The formalism is experimentally verified and accounts for the asymmetric lineshapes arising from the interaction between magnon and photon channels. As the magnon–photon coupling strength is increased, these channels merge into hybridized magnon–photon modes and the generalized Fano interference picture breaks down. Our results are universally applicable to systems underlying the linearized Jaynes-Cummings Hamiltonian at low cooperativity and connect the microscopic parameters of the quantum optical model to generalized Fano lineshapes.

Realizing room-temperature strong coupling of single-exciton with plasmons by controlling quantum exceptional point

Single-exciton strong coupling with plasmons is highly desirable for exploiting room-temperature quantum devices and applications. However, the large plasmon decay makes the realization of such strong coupling extremely difficult. To overcome this challenge, here we propose an effective approach to easily achieve the single-exciton strong coupling at room temperature by controlling quantum exceptional point (QEP) of the coupling system via matching the decay between the localized plasmon mode (LPM) and exciton. The good match can be reached by suppressing the LPM’s decay with the use of a leaky Fabry-Perot cavity. Experimental results show that the LPM’s decay linewidth is greatly compressed from ~ 45 nm to ~ 15 nm, which is close to the excitonic linewidth (~ 10 nm), pushing their interaction from the Fano interference into the strong coupling. Our work opens a new way to flexibly control the QEP and more easily realize the single-exciton strong coupling in ambient conditions.