Abstract: We theoretically investigate, through Ginzburg?Landau simulations, the possibility to induce an open circuit voltage in absence of applied current, by dragging superconducting vortices with a dynamic pinning array as for instance that created by a nearby sliding vortex lattice or moving laser spots. Different dynamic regimes, such as synchronous vortex motion or dynamic vortex chains consisting of laggard vortices, can be observed by varying the velocity of the sliding pinning potential and the applied magnetic field. Additionally, due to the edge barrier, significantly different induced voltage is found depending on whether the vortices are dragged along the superconducting strip or perpendicular to the lateral edges. The output voltage in the proposed mesoscopic superconducting dynamo can be tuned by varying size, density and directions of the sliding pinning potential.

Abstract: The electrochemical reduction of CO2 to multi-carbon products has attracted much attention because it provides an avenue to the synthesis of value-added carbon-based fuels and feedstocks using renewable electricity. Unfortunately, the efficiency of CO2 conversion to C-2 products remains below that necessary for its implementation at scale. Modifying the local electronic structure of copper with positive valence sites has been predicted to boost conversion to C-2 products. Here, we use boron to tune the ratio of Cu delta+ to Cu-0 active sites and improve both stability and C-2-product generation. Simulations show that the ability to tune the average oxidation state of copper enables control over CO adsorption and dimerization, and makes it possible to implement a preference for the electrosynthesis of C-2 products. We report experimentally a C-2 Faradaic efficiency of 79 +/- 2% on boron-doped copper catalysts and further show that boron doping leads to catalysts that are stable for in excess of similar to 40 hours while electrochemically reducing CO2 to multi-carbon hydrocarbons.

Abstract: The graphene-metal contact is very important for optimizing the performance of graphene based electronic devices. However, it is difficult to probe the properties of the graphene/metal interface directly via transport measurements in traditional graphene lateral devices, because the dominated transport channel is graphene, not the interface. Here, we employ the Au/graphene/Au vertical and lateral hybrid structure to unveil the metal-graphene interface properties, where the transport is dominated by the charge carriers across the interface. The magnetoresistance (MR) of Au/monolayer graphene/Au and Au/stacked two-layered graphene/Au devices is measured and modulated by gate voltage, demonstrating that the interface is a device. The gate-tunable MR is identified from the graphene lying on the SiO2 substrate and underneath the top metal electrode. Our unique structures couple the in-plane and out-of-plane transport and display linear MR with small amplitude oscillations at low temperatures. Under a magnetic field, the electronic coupling between the graphene edge states and the electrode leads to the appearance of quantum oscillations. Our results not only provide a new pathway to explore the intrinsic transport mechanism at the graphene/metal interface but also open up new vistas of magnetoelectronics.