Study of graphene p-n junctions formed by the electrostatic modification of the SiO substrate.

We study the transport properties of mm-scale CVD graphene p-n junctions, which are formed in a single gated graphene field effect transistor configuration. Here, an electrical-stressing-voltage technique served to modify the electrostatic potential in the SiO/Si substrate and create the p-n junction. We examine the transport characteristics about the Dirac points that are localized in the perturbed and unperturbed regions in the graphene channel and note the quantitative differences in the Hall effect between the perturbed and unperturbed regions.

Size dependence- and induced transformations- of fractional quantum Hall effects under tilted magnetic fields.

Two-dimensional electron systems subjected to high transverse magnetic fields can exhibit Fractional Quantum Hall Effects (FQHE). In the GaAs/AlGaAs 2D electron system, a double degeneracy of Landau levels due to electron-spin, is removed by a small Zeeman spin splitting, [Formula: see text], comparable to the correlation energy. Then, a change of the Zeeman splitting relative to the correlation energy can lead to a re-ordering between spin polarized, partially polarized, and unpolarized many body ground states at a constant filling factor.

Marginal metallic state at a fractional filling of '8/5' and '4/3' of Landau levels in the GaAs/AlGaAs 2D electron system.

A metallic state with a vanishing activation gap, at a filling factor [Formula: see text] in the untilted specimen with [Formula: see text], and at [Formula: see text] at [Formula: see text] under a [Formula: see text] tilted magnetic field, is examined through a microwave photo-excited transport study of the GaAs/AlGaAs 2 dimensional electron system (2DES). The results presented here suggest, remarkably, that at the possible degeneracy point of states with different spin polarization, where the 8/5 or 4/3 FQHE vanish, there occurs a peculiar marginal metallic state that differs qualitatively from a quantum Hall insulating state and the usual quantum Hall metallic state. Such a marginal metallic state occurs most prominently at [Formula: see text], and at [Formula: see text] under tilt as mentioned above, over the interval [Formula: see text], that also includes the [Formula: see text] state, which appears perceptibly gapped in the first instance.

Jumping In and Out of the Phase Diagram Using Electric Fields: Time Scale for Remixing of Polystyrene/Poly(vinyl methyl ether) Blends.

We demonstrate it is possible to repeatedly jump polystyrene (PS)/poly(vinyl methyl ether) (PVME) blends from the one-phase to two-phase region by simply turning on and off an electric field at a fixed temperature near the phase boundary. This builds on our previous work that established electric fields enhance the miscibility of PS/PVME blends by shifting the phase separation temperature () of 50/50 blends up by 13.5 ± 1.

Electric fields enhance miscibility of polystyrene/poly(vinyl methyl ether) blends.

How the presence of electric fields alters the miscibility of mixtures has been studied since the 1960s with conflicting reports on both the magnitude and direction of the shift in the phase separation temperature Ts. Theoretical understanding of the phenomenon has been hampered by the lack of experimental data with unambiguously large shifts in Ts outside of experimental error. Here, we address these concerns by presenting data showing that uniform electric fields strongly enhance the miscibility of polystyrene (PS)/poly(vinyl methyl ether) (PVME) blends.