in the city of New York, USA 4 Samsung-SKKU Graphene Center (SSGC), Suwon, Gyeonggi 440-746, Korea †These authors contributed equally to this work Oscillators, which produce continuous periodic signals from direct current power, are central to modern communications systems, with versatile applications such as timing references and frequency modulators 1-7 . However, conventional oscillators typically consist of macroscopic mechanical resonators such as quartz crystals, which require excessive off-chip space. Here we report oscillators built on micron-size, atomically-thin graphene nanomechanical resonators, whose frequencies can be electrostatically tuned by as much as 14%.The self-sustaining mechanical motion of the oscillators is generated and transduced at room temperature by simple electrical circuitry. The prototype graphene voltage controlled oscillators exhibit frequency stability and modulation bandwidth sufficient for modulation of radio-frequency carrier signals. As a demonstration, we employ a graphene oscillator as the active element for frequency modulated signal generation, and achieve efficient audio signal transmission. 1 arXiv:1612.04019v1 [cond-mat.mes-hall]

Electron-electron interactions strongly affect the behavior of low-dimensional systems. In one dimension (1D), arbitrarily weak interactions qualitatively alter the ground state producing a Luttinger liquid (LL) 1 which has now been observed in a number of experimental systems 2-6 . Interactions are even more important at low carrier density, and in the limit when the long-ranged Coulomb potential is the dominant energy scale, the electron liquid is expected to become a periodically ordered solid known as the Wigner crystal 7 . In 1D, the Wigner crystal has been predicted to exhibit novel spin and magnetic properties not present in an ordinary LL 8-12 . However, despite recent progress in coupled quantum wires 13, 14 , unambiguous experimental demonstration of this state has not been possible due to the role of disorder. Here, we demonstrate using low-temperature single-electron transport spectroscopy that a hole gas in low-disorder carbon nanotubes with a band gap is a realization of the 1D Wigner crystal. Our observation can lead to unprecedented control over the behavior of the spatially separated system of carriers, and could be used to realize solid state quantum computing with long coherence times. Carbon nanotubes are high mobility quantum wires that may enable the study of the intrinsic properties of the 1D electron gas without interference from disorder. Single quantum-dot transport experiments have been performed, demonstrating Coulomb blockade 15, 16 and Kondo physics 17 , down to the few-electron-hole regime 18-20 . These experiments have generally been interpreted

Recently the hybrid organic-inorganic trihalide perovskites have shown remarkable performance as active layers in photovoltaic and other optoelectronic devices. However, their spin characteristic properties have not been fully studied, although due to the relatively large spin-orbit coupling these materials may show great promise for spintronic applications. Here we demonstrate spin-polarized carrier injection into methylammonium lead bromide films from metallic ferromagnetic electrodes in two spintronic-based devices: a ‘spin light emitting diode’ that results in circularly polarized electroluminescence emission; and a ‘vertical spin valve’ that shows giant magnetoresistance. In addition, we also apply a magnetic field perpendicular to the injected spins orientation for measuring the ‘Hanle effect’, from which we obtain a relatively long spin lifetime for the electrically injected carriers. Our measurements initiate the field of hybrid perovskites spin-related optoelectronic applications.

Even though bulk metallic systems contain a very large number of strongly interacting electrons, their properties are well described within Landau's Fermi liquid theory of non-interacting quasiparticles. Although many higher-dimensional systems can be successfully understood on the basis of such non-interacting theories, this is not possible for one-dimensional systems. When confined to narrow channels, electron interaction gives rise to such exotic phenomena as spin-charge separation and the emergence of correlated-electron insulators. Such strongly correlated electronic behaviour has recently been seen in experiments on one-dimensional carbon nanotubes and nanowires, and this behaviour challenges the theoretical description of such systems.

A family of 2D coordination polymers were successfully synthesized through "bottom-up" techniques using Ni, Cu, Co, and hexaaminobenzene. Liquid-liquid and air-liquid interfacial reactions were used to realize thick (∼1-2 μm) and thin (<10 nm) stacked layers of nanosheet, respectively. Atomic-force microscopy and scanning electron microscopy both revealed the smooth and flat nature of the nanosheets. Selected area diffraction was used to elucidate the hexagonal crystal structure of the framework. Electronic devices were fabricated on thin samples of the Ni analogue and they were found to be mildly conducting and also showed back gate dependent conductance.