Edge States and Quantum Hall Effect in Graphene under a Modulated Magnetic Field

Graphene properties can be manipulated by a periodic potential. Based on the tight-binding model, we study graphene under a one-dimensional (1D) modulated magnetic field which contains both a uniform and a staggered component. New chiral current-carrying edge states are generated at the interfaces where the staggered component changes direction. These edge states lead to an unusual integer quantum Hall effect (QHE) in graphene, which can be observed experimentally by a standard four-terminal Hall measurement. When Zeeman spin splitting is considered, a novel state is predicted where the electron edge currents with opposite polarization propagate in the opposite directions at one sample boundary, whereas propagate in the same directions at the other sample boundary.Comment: 5 pages, 4 figure

Ceramic Sensors for Wireless High-Temperature Sensing

A RF resonator for sensing a physical or environmental parameter includes a substrate having a substrate surface. A polymer-derived ceramic (PDC) element is positioned on or within the substrate surface. The RF resonator has a resonant frequency that changes as a function of the physical or environmental parameter. A system for wirelessely sensing at least one physical or environmental parameter includes at least one RF resonator and a wireless RF reader located remotely from the RF resonator first transmitting a wide-band RF interrogation signal that excites the RF resonator. The wireless RF reader detects a sensing signal retransmitted by the RF resonator and includes a processor for determining the physical or environmental parameter at the location of the RF resonator from the sensing signal

(Photo)Electrocatalytic CO2 Reduction at the Defective Anatase TiO2 (101) Surface

Excessive carbon dioxide (CO2) emissions by combustion of fossil fuels are linked to global warming and rapid climate change. One promising route to lowering the concentration of CO2 in the atmosphere is to reduce it to useful small molecules via photoelectrocatalytic hydrogenation, which would enable solar energy storage with a zero-carbon emission cycle and perform a more efficient separation of the photogenerated electron and hole pair than pure photocatalysis. Indeed, photoelectrocatalytic CO2 reduction has been an intense focus of research. Using the density functional theory (DFT), we studied the CO2 reduction reaction on the defective anatase TiO2 (101) surface, at both the solvent/catalyst and the electrolyte/catalyst interfaces. The analysis of the electronic structure of the surface shows a contrast between the solvent/catalyst and the electrolyte/catalyst interfaces, which results in the two corresponding catalytic cycles being distinct. Our study explains at the electronic and mechanistic levels why methanol is the main product in the presence of the electrolyte and why the overpotential is not only controlled by the reaction process but also by the diffusion process

Generating Many Majorana Modes via Periodic Driving: A Superconductor Model

Realizing Majorana modes (MMs) in condensed-matter systems is of vast experimental and theoretical interests, and some signatures of MMs have been measured already. To facilitate future experimental observations and to explore further applications of MMs, generating many MMs at ease in an experimentally accessible manner has become one important issue. This task is achieved here in a one-dimensional $p$-wave superconductor system with the nearest- and next-nearest-neighbor interactions. In particular, a periodic modulation of some system parameters can induce an effective long-range interaction (as suggested by the Baker-Campbell-Hausdorff formula) and may recover time-reversal symmetry already broken in undriven cases. By exploiting these two independent mechanisms at once we have established a general method in generating many Floquet MMs via periodic driving.Comment: 5 pages, 3 figures. To appear in Phys. Rev. B as a Rapid Communicatio