Multi-state and non-volatile control of graphene conductivity with surface electric fields

Planar electrodes patterned on a ferroelectric substrate are shown to provide lateral control of the conductive state of a two-terminal graphene stripe. A multi-level and on-demand memory control of the graphene resistance state is demonstrated under low sub-coercive electric fields, with a susceptibility exceeding by more than two orders of magnitude those reported in a vertical gating geometry. Our example of reversible and low-power lateral control over 11 memory states in the graphene conductivity illustrates the possibility of multimemory and multifunctional applications, as top and bottom inputs remain accessible.Comment: Graphene ferroelectric lateral structure for multi-state and non-volatile conductivity control, 4 pages, 4 figure

Light controlled magnetoresistance and magnetic field controlled photoresistance in CoFe film deposited on BiFeO3

We present a magnetoresistive-photoresistive device based on the interaction of a piezomagnetic CoFe thin film with a photostrictive BiFeO3 substrate that undergoes light-induced strain. The magnitude of the resistance and magnetoresistance in the CoFe film can be controlled by the wavelength of the incident light on the BiFeO3. Moreover, a light-induced decrease in anisotropic magnetoresistance is detected due to an additional magnetoelastic contribution to magnetic anisotropy of the CoFe film. This effect may find applications in photo-sensing systems, wavelength detectors and can possibly open a research development in light-controlled magnetic switching properties for next generation magnetoresistive memory devices.Comment: 5 pages, 4 figures, journal pape

Three terminal capacitance technique for magnetostriction and thermal expansion measurements

An instrument has been constructed to measure a large range of magnetostriction and thermal expansion between room temperature and 4 K in a superconductive split-coil magnet, that allows investigation in magnetic fields up to 12 T. The very small bulk samples (up to 1 mm in size) as well as big ones (up to 13 mm) of the irregular form can be measured. The possibility of magnetostriction investigation in thin films is shown. A general account is given of both electrical and the mechanical aspects of the design of capacitance cell and their associated electronic circuitry. A simple lever device is proposed to increase the sensitivity twice. The resulting obtained sensitivity can be 0.5 Angstrom. The performance of the technique is illustrated by some preliminary measurements of the magnetostriction of superconducting MgB2, thermal expansion of (La0.8Ba0.2)0.93MnO3 single crystal and magnetoelastic behavior of the Ni/Si(111) and La0.7Sr0.3CoO3/SAT0.7CAT0.1LA0.2(001) cantilevers.Comment: 6 pages, 6 figures, journal pape

Superconductivity in Ca-doped graphene

Graphene, a zero-gap semimetal, can be transformed into a metallic, semiconducting or insulating state by either physical or chemical modification. Superconductivity is conspicuously missing among these states despite considerable experimental efforts as well as many theoretical proposals. Here, we report superconductivity in calcium-decorated graphene achieved by intercalation of graphene laminates that consist of well separated and electronically decoupled graphene crystals. In contrast to intercalated graphite, we find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among intercalants used in our experiments such as potassium, caesium and lithium. Ca-decorated graphene becomes superconducting at ~ 6 K and the transition temperature is found to be strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration. In addition to the first evidence for superconducting graphene, our work shows a possibility of inducing and studying superconductivity in other 2D materials using their laminates

Multi-state and non-volatile control of graphene conductivity with surface electric fields

Planar electrodes patterned on a ferroelectric substrate are shown to provide lateral control of the conductive state of a two-terminal graphene stripe. A multi-level and on-demand memory control of the graphene resistance state is demonstrated under low sub-coercive electric fields, with a susceptibility exceeding by more than two orders of magnitude those reported in a vertical gating geometry. Our example of reversible and low-power lateral control over 11 memory states in the graphene conductivity illustrates the possibility of multimemory and multifunctional applications, as top and bottom inputs remain accessible. (C) 2015 AIP Publishing LLC

Quantum teleportation on a photonic chip

Quantum teleportation is a fundamental concept in quantum physics which now finds important applications at the heart of quantum technology including quantum relays, quantum repeaters and linear optics quantum computing (LOQC). Photonic implementations have largely focussed on achieving long distance teleportation due to its suitability for decoherence-free communication. Teleportation also plays a vital role in the scalability of photonic quantum computing, for which large linear optical networks will likely require an integrated architecture. Here we report the first demonstration of quantum teleportation in which all key parts - entanglement preparation, Bell-state analysis and quantum state tomography - are performed on a reconfigurable integrated photonic chip. We also show that a novel element-wise characterisation method is critical to mitigate component errors, a key technique which will become increasingly important as integrated circuits reach higher complexities necessary for quantum enhanced operation.Comment: Originally submitted version - refer to online journal for accepted manuscript; Nature Photonics (2014

Nanomechanical electro-optical modulator based on atomic heterostructures

Two-dimensional atomic heterostructures combined with metallic nanostructures allow one to realize strong light–matter interactions. Metallic nanostructures possess plasmonic resonances that can be modulated by graphene gating. In particular, spectrally narrow plasmon resonances potentially allow for very high graphene-enabled modulation depth. However, the modulation depths achieved with this approach have so far been low and the modulation wavelength range limited. Here we demonstrate a device in which a graphene/hexagonal boron nitride heterostructure is suspended over a gold nanostripe array. A gate voltage across these devices alters the location of the two-dimensional crystals, creating strong optical modulation of its reflection spectra at multiple wavelengths: in ultraviolet Fabry–Perot resonances, in visible and near-infrared diffraction-coupled plasmonic resonances and in the mid-infrared range of hexagonal boron nitride's upper Reststrahlen band. Devices can be extremely subwavelength in thickness and exhibit compact and truly broadband modulation of optical signals using heterostructures of two-dimensional materials