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Metamaterials‐based sensors are of primary interest in physics, materials science, medicine, and biophysics thanks to their ability to detect very tiny amount of molecules spread into a medium. Here, a metastructure utilizing the epsilon near zero (εNZ) and Fano–Rabi physics is engineered to design a system with ultra‐high sensitivity. So far, a dedicated study of such systems has been missing. In this work, the authors report the results of their efforts to fill the gap by considering a metasurface, designed as a periodical array of rings with a cross in their center, placed on top of a silver (Ag) and zinc oxide (ZnO) epsilon near‐zero optical nanocavity (εNZ‐ONC) metamaterial. The accurate selection of the metasurface parameters allows the design of a sensor exhibiting an extremely high sensitivity of about 16 000 and 21 000 nm RIU−1 depending on incoming polarization. This work paves the way for the development of novel groundbreaking devices for biomedical and environmental application based on plasmonic and photonic design principles. [ABSTRACT FROM AUTHOR]

We find quantum states that are spatially localized by two potential barriers due to commensurability between the total length of the system and the distance between the barriers. Such states are resonant because they coexist with nearly continuum states, as found in the present one-dimensional Schrödinger equation investigation. They exist even in the case of weak and thin barriers, and we discuss them here in the context of conducting films made by bismuth whose mean free path is abnormally large. • The main outcome is the obtainment of resonanting quantum states that are spatially localized due to the commensurability between the two basic lengths of the system. • This is a study of the one-dimensional Schrödinger equation with two finite-height barriers inside an infinite potential well. • We analized them in the context of films, where they provide a way to confine states between insulating thin layers. We chose bismuth films because of the abnormally long mean free path of this element. • Three interesting examples are studied where two of them show a stable coexistence between bound states and nearly free states, sustained by a weak and thin set of barriers. • For the set of parameters chosen here, we find that the transitions between the resonanting states fall in the terahertz range, a frequency range of particular interest for technological applications. [ABSTRACT FROM AUTHOR]

Recently, the transformation from random to chaotic behavior in the statistics of Fano–Feshbach resonances was observed in thulium atoms with rising ensemble temperature. We performed random matrix theory simulations of such spectra and analyzed the resulting statistics in an attempt to understand the mechanism of the transformation. Our simulations show that, when evaluated in terms of the Brody parameter, resonance statistics do not change or change insignificantly when higher temperature resonances are appended to the statistics. In the experiments evaluated, temperature was changed simultaneously with optical dipole trap depth. Thus, simulations included the Stark shift based on the known polarizability of the free atoms and assuming their polarizability remains the same in the bound state. Somewhat surprisingly, we found that, while including the Stark shift does lead to minor statistical changes, it does not change the resonance statistics and, therefore, is not responsible for the experimentally observed statistic transformation. This observation suggests that either our assumption regarding the polarizability of Feshbach molecules is poor or that an additional mechanism changes the statistics and leads to more chaotic statistical behavior.

Recently, the transformation from random to chaotic behavior in the statistics of Fano–Feshbach resonances was observed in thulium atoms with rising ensemble temperature. We performed random matrix theory simulations of such spectra and analyzed the resulting statistics in an attempt to understand the mechanism of the transformation. Our simulations show that, when evaluated in terms of the Brody parameter, resonance statistics do not change or change insignificantly when higher temperature resonances are appended to the statistics. In the experiments evaluated, temperature was changed simultaneously with optical dipole trap depth. Thus, simulations included the Stark shift based on the known polarizability of the free atoms and assuming their polarizability remains the same in the bound state. Somewhat surprisingly, we found that, while including the Stark shift does lead to minor statistical changes, it does not change the resonance statistics and, therefore, is not responsible for the experimentally observed statistic transformation. This observation suggests that either our assumption regarding the polarizability of Feshbach molecules is poor or that an additional mechanism changes the statistics and leads to more chaotic statistical behavior. [ABSTRACT FROM AUTHOR]