Infrared Fingerprints of Natural 2D Talc and Plasmon-Phonon Coupling in Graphene-Talc Heterostructures

Two-dimensional (2D) materials occupy a noteworthy place in nanophotonics providing for subwavelength light confinement and optical phenomena dissimilar to those of their bulk counterparts. In the mid-infrared, graphene-based heterostructures and van der Waals crystals of hexagonal boron nitride (hBN) overwhelmingly concentrate the attention by exhibiting real-space nano-optics features from plasmons, phonon-polaritons, and hybrid plasmon phonon-polaritons. Here we present a prime study on mid-infrared nanophotonics of talc, a natural atomically flat layered material, and graphene-talc (G-talc) heterostructures using broadband synchrotron infrared nanospectroscopy. Wavelength tuning of the talc vibrational resonances, assigned to in- and out-of-plane molecular vibrations, are achieved by changing the thickness of the crystals, which configures a tunable infrared signature for the 2D talc. In G-talc nanostructures, we unveil a coupling of the graphene plasmons polaritons with surface phonons polaritons of talc, originating hybrid surface plasmon-phonon polaritons modes. In analogy to G-hBN and G-SiO2 heterostructures, the coupling in G-talc produces a large increase in the opto-vibrational activity for the out-of-plane mode as well as it induces a blue-shift for the in-plane mode. Moreover, the coupling can be modulated by an external gate voltage to the heterostructure when mounted in a transistor configuration. Therefore, our results introduce talc and G-talc heterostructures as appealing materials for nanophotonics, especially for applications involving long wavelengths and active electric tuning of opto-vibrational activity

Gate controlled Aharonov-Bohm-type oscillations from single neutral excitons in quantum rings

We report on a magnetophotoluminescence study of single self-assembled semiconductor nanorings which are fabricated by molecular-beam epitaxy combined with AsBr3 in situ etching. Oscillations in the neutral exciton radiative recombination energy and in the emission intensity are observed under an applied magnetic field. Further, we control the period of the oscillations with a gate potential that modifies the exciton confinement. We infer from the experimental results, combined with calculations, that the exciton Aharonov-Bohm effect may account for the observed effects

Free-standing Fe2O3 nanomembranes enabling ultra-long cycling life and high rate capability for Li-ion batteries

With Fe(2)O(3) as a proof-of-concept, free-standing nanomembrane structure is demonstrated to be highly advantageous to improve the performance of Li-ion batteries. The Fe(2)O(3) nanomembrane electrodes exhibit ultra-long cycling life at high current rates with satisfactory capacity (808 mAh g(−1) after 1000 cycles at 2 C and 530 mAh g(−1) after 3000 cycles at 6 C) as well as repeatable high rate capability up to 50 C. The excellent performance benefits particularly from the unique structural advantages of the nanomembranes. The mechanical feature can buffer the strain of lithiation/delithiation to postpone the pulverization. The two-dimensional transport pathways in between the nanomembranes can promote the pseudo-capacitive type storage. The parallel-laid nanomembranes, which are coated by polymeric gel-like film and SEI layer with the electrolyte in between layers, electrochemically behave like numerous “mini-capacitors” to provide the pseudo-capacitance thus maintain the capacity at high rate