More Like this

1. High-sensitivity in various gyrator-based circuits with exceptional points of degeneracy

   https://doi.org/10.1051/epjam/2022005  

   Rouhi, Kasra; Nikzamir, Alireza; Figotin, Alexander; Capolino, Filippo (January 2022, EPJ Applied Metamaterials)

   Mann, Sander; Vellucci, Stefano (Ed.)

   Exceptional points of degeneracy (EPD) can enhance the sensitivity of circuits by orders of magnitude. We show various configurations of coupled LC resonators via a gyrator that support EPDs of second and third-order. Each resonator includes a capacitor and inductor with a positive or negative value, and the corresponding EPD frequency could be real or imaginary. When a perturbation occurs in the second-order EPD gyrator-based circuit, we show that there are two real-valued frequencies shifted from the EPD one, following a square root law. This is contrary to what happens in a Parity-Time (PT) symmetric circuits where the two perturbed resonances are complex valued. We show how to get a stable EPD by coupling two unstable resonators, how to get an unstable EPD with an imaginary frequency, and how to get an EPD with a real frequency using an asymmetric gyrator. The relevant Puiseux fractional power series expansion shows the EPD occurrence and the circuit's sensitivity to perturbations. Our findings pave the way for new types of high-sensitive devices that can be used to sense physical, chemical, or biological changes. 

   more » « less
2. Electromagnetically induced transparency and lattice resonances in metasurfaces composed of silicon nanocylinders

   Jamilan, S.; Semouchkin, G.; Gandji, N.; Semouchkina, E. (July 2019, 7th Advanced Electromagnetics Symposium, Lisbon, Portugal)

   Densely packed metasurfaces composed of cylindrical silicon nano-resonators were found to demonstrate the phenomenon of electromagnetically induced transparency at electric dipolar resonances. It was shown that this phenomenon is not related to overlapping of dipolar resonances or to the Kerker’s effects. The observed transparency appeared to be related to interference between waves scattered by nano-resonators and by additional scattering centers including the electric branch of lattice resonances. Coupled resonance fields were also found to contribute to observed phenomena. 

   more » « less
3. Plasmon-induced coherence, exciton-induced transparency, and Fano interference for hybrid plasmonic systems in strong coupling regime

   https://doi.org/10.1063/5.0083197  

   Scott, Zoe; Muhammad, Shafi; Shahbazyan, Tigran V. (May 2022, The Journal of Chemical Physics)

   We present an analytical model describing the transition to a strong coupling regime for an ensemble of emitters resonantly coupled to a localized surface plasmon in a metal–dielectric structure. The response of a hybrid system to an external field is determined by two distinct mechanisms involving collective states of emitters interacting with the plasmon mode. The first mechanism is the near-field coupling between the bright collective state and the plasmon mode, which underpins the energy exchange between the system components and gives rise to exciton-induced transparency minimum in scattering spectra in the weak coupling regime and to emergence of polaritonic bands as the system transitions to the strong coupling regime. The second mechanism is the Fano interference between the plasmon dipole moment and the plasmon-induced dipole moment of the bright collective state as the hybrid system interacts with the radiation field. The latter mechanism is greatly facilitated by plasmon-induced coherence in a system with the characteristic size below the diffraction limit as the individual emitters comprising the collective state are driven by the same alternating plasmon near field and, therefore, all oscillate in phase. This cooperative effect leads to scaling of the Fano asymmetry parameter and of the Fano function amplitude with the ensemble size, and therefore, it strongly affects the shape of scattering spectra for large ensembles. Specifically, with increasing emitter numbers, the Fano interference leads to a spectral weight shift toward the lower energy polaritonic band. 

   more » « less
4. Transition to strong coupling regime in hybrid plasmonic systems: Exciton-induced transparency and Fano interference

   Shahbazyan, Tigran V. (January 2021, arXiv)

   null (Ed.)

   We present a microscopic model describing the transition to 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 the transition to strong coupling regime. The second mechanism is 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. 

   more » « less
5. Asymmetric Lineshapes of Efimov Resonances in Mass-Imbalanced Ultracold Gases

   https://doi.org/10.3390/atoms9040110  

   Giannakeas, Panagiotis; Greene, Chris H. (December 2021, Atoms)

   The resonant profile of the rate coefficient for three-body recombination into a shallow dimer is investigated for mass-imbalanced systems. In the low-energy limit, three atoms collide with zero-range interactions, in a regime where the scattering lengths of the heavy–heavy and the heavy–light subsystems are positive and negative, respectively. For this physical system, the adiabatic hyperspherical representation is combined with a fully semi-classical method and we show that the shallow dimer recombination spectra display an asymmetric lineshape that originates from the coexistence of Efimov resonances with Stückelberg interference minima. These asymmetric lineshapes are quantified utilizing the Fano profile formula. In particular, a closed-form expression is derived that describes the width of the corresponding Efimov resonances and the Fano lineshape asymmetry parameter q. The profile of Efimov resonances exhibits a q-reversal effect as the inter- and intra-species scattering lengths vary. In the case of a diverging asymmetry parameter, i.e., |q|→∞, we show that the Efimov resonances possess zero width and are fully decoupled from the three-body and atom–dimer continua, and the corresponding Efimov metastable states behave as bound levels. 

   more » « less