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We experimentally demonstrate primordial metamaterials - composite media supporting essentially nonlocal wave propagation, grown with molecular beam epitaxy. Our transmission measurements confirm the theoretically predicted spectral signature of coupling to nonlocal modes. 

An interspersed array of Cs and Rb atoms was used to implement a protocol for the correction of correlated errors. 

The incorporation of dilute concentrations of bismuth into traditional III–V alloys produces significant reductions in bandgap energy presenting unique opportunities in strain and bandgap engineering. However, the disparity between the ideal growth conditions for the host matrix and those required for substitutional bismuth incorporation has caused the material quality of these III–V–Bi alloys to lag behind that of conventional III–V semiconductors. InSb1−xBix, while experimentally underexplored, is a promising candidate for high-quality III–V–Bi alloys due to the relatively similar ideal growth temperatures for InSb and III–Bi materials. By identifying a highly kinetically limited growth regime, we demonstrate the growth of high-quality InSb1−xBix by molecular beam epitaxy. X-ray diffraction and Rutherford backscattering spectrometry (RBS) measurements of the alloy's bismuth concentration, coupled with smooth surface morphologies as measured by atomic force microscopy, suggest unity-sticking bismuth incorporation for a range of bismuth concentrations from 0.8% to 1.5% as measured by RBS. In addition, the first photoluminescence was observed from InSb1−xBix and demonstrated wavelength extension up to 7.6 μm at 230 K, with a bismuth-induced bandgap reduction of ∼29 meV/% Bi. Furthermore, we report the temperature dependence of the bandgap of InSb1−xBix and observed behavior consistent with that of a traditional III–V alloy. The results presented highlight the potential of InSb1−xBix as an alternative emerging candidate for accessing the longwave-infrared. 

Highly mismatched semiconductor alloys (HMAs) offer unusual combinations of bandgap and lattice constant, which are attractive for myriad applications. Dilute borides, such as BGa(In)As, are typically assumed to be HMAs. BGa(In)As can be grown in higher alloy compositions than Ga(In)NAs with comparable bandgaps, potentially enabling routes to lattice-matched telecom lasers on Si or GaAs. However, BGa(In)As remains relatively unexplored, especially with large fractions of indium. Density functional theory with HSE06 hybrid functionals was employed to study BGaInAs with 4%–44% In and 0%–11% B, including atomic rearrangement effects. All compositions showed a direct bandgap, and the character of the lowest conduction band was nearly unperturbed with the addition of B. Surprisingly, although the bandgap remained almost constant and the lattice constant followed Vegard's law with the addition of boron, the electron effective mass increased. The increase in electron effective mass was higher than in conventional alloys, though smaller than those characteristics of HMAs. This illustrates a particularly striking finding, specifically that the compositional space of BGa(In)As appears to span conventional alloy and HMA behavior, so it is not well-described by either limit. For example, adding B to GaAs introduces additional states within the conduction band, but further addition of In removes them, regardless of the atomic arrangement.