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We investigated Goos–Hänchen (GH) and Imbert–Fedorov (IF) shifts of a reflective beam on a twisted bilayer of hexagonal boron nitride (hBN), where a left circularly polarized beam was incident on the surface. Our results demonstrate that the twist angle between the two optical axes plays an important role in obtaining large shifts with a high reflectivity. The GH shift with 10λ 0 is achieved, while the reflectivity is near 100% by tuning the twist angle. The maximum of the IF shift is found in the certain condition satisfied by the reflective coefficients, and the shift strongly depends on the twist angle between the optical axes of the two slabs. The spatial shifts obtained directly from the GH and IF shift definitions were provided, which indicate that the theoretical results from the stationary phase method are believable. These results may open up a new way for developing the nano-optical devices.

Superconducting properties were studied on high quality superconductors (T c = 39 K) and (T c = 44 K) prepared by intercalating Ba/Sr atoms into tetragonal β-FeSe by liquid ammonia. The elongated c-axis and almost unchanged a-axis of , compared with β-FeSe, suggests an unchanged intra--layer structure and the T c enhancement is due to a 3D to 2D-like Fermi surface transformation. The superconducting coherent lengths ξ(0), the Ginzburg–Landau parameters κ and penetration depths λ(0) obtained from the extrapolated lower and upper critical fields B c1(0) and B c2(0) indicate that both compounds are typical type-II superconductors. The temperature dependence of 1/(T) of deduced from the low-field magnetic susceptibility shows a two-gap s-wave behavior with superconducting gaps of = 6.47 meV and = 1.06 meV.