Carlos Wexler

Theory of the breakdown of the quantum Hall effect

Breakdown of the Quantum Hall Effect at high values of injected current is explained as a consequence of an abrupt formation of a metallic ``river percolating from one edge of the sample to the other. Such river is formed when lakes of compressible liquid, where the long-range disorder potential is screened, get connected with each other due to the strong electric field. Our theory predicts critical currents consistent with experiment values and explains various features of the breakdown.

MAGNUS AND IORDANSKII FORCES IN SUPERFLUIDS

The transverse force acting on a quantized vortex in a superfluid is a problem that has eluded a complete understanding for more than three decades. In this Letter I calculate the {ital superfluid } velocity part of the transverse force in a way closely related to Laughlin{close_quote}s argument for the quantization of conductance in the quantum Hall effect. A combination of this result, the {ital vortex} velocity part of the transverse force found by Thouless, Ao, and Niu [Phys.Rev.Lett.{bold 76}, 3758 (1996)], and Galilean invariance shows that there cannot be a transverse force proportional to the normal fluid velocity. {copyright} {ital 1997} {ital The American Physical Society}

Behavior of hexane on graphite at near-monolayer densities: Molecular dynamics study

We present the results of molecular dynamics (MD) studies of hexane physisorbed onto graphite for eight coverages in the range

Adsorption by design: Tuning atom-graphene van der Waals interactions via mechanical strain

0.875 le rho le 1.05

Quantum Hall Effect: Current distribution and the role of measurement

(in units of monolayers). At low temperatures the adsorbate molecules form a uniaxially incommensurate herringbone (UI-HB) solid. At high coverages the solid consists of adsorbate molecules that are primarily rolled on their side perpen-dicular to the surface of the substrate. As the coverage is decreased, the amount of molecular rolling diminishes until

QUANTIZED VORTICES IN SUPERFLUIDS AND SUPERCONDUCTORS

rho

TRANSVERSE FORCE ON A QUANTIZED VORTEX IN A SUPERCONDUCTOR

= 0.933 where it disappears (molecules become primarily parallel to the surface). If the density is decreased enough, vacancies appear. As the temperature is increased we observe a three-phase regime for

New Pathways and Metrics for Enhanced, Reversible Hydrogen Storage in Boron-Doped Carbon Nanospaces

rho>0.933

COMMENT ON: MAGNUS AND IORDANSKII FORCES IN SUPERFLUIDS. AUTHORS' REPLY

(with an orientationally ordered nematic mesophase), for lower coverages the system melts directly to the disordered (and isotropic) liquid phase. The solid-nematic transition temperature is very sensitive to coverage whereas the melting temperature is quite insensitive to it, except for at low coverages where increased in-plane space and ultimately vacancies soften the solid phase and lower the melting temperature. Our results signal the importance of molecular rolling and tilting (which result from an the competition between molecule-molecule and molecule-substrate interactions) for the formation of the intermediate phase, while the insensitivity of the systems melting temperature to changing density is understood in terms of in-plane space occupation through rolling. Comparisons and contrasts with experimental results are discussed.

COMMENT ON: BERRY'S PHASE AND THE MAGNUS FORCE FOR A VORTEX LINE IN A SUPERCONDUCTOR, TRANSVERSE FORCE ON A QUANTIZED VORTEX IN A SUPERFLUID, AND MAGNUS AND IORDANSKII FORCES IN SUPERFLUIDS. AUTHORS' REPLY

We aim to understand how the van der Waals force between neutral adatoms and a graphene layer is modified by uniaxial strain and electron correlation effects. A detailed analysis is presented for three atoms (He, H, and Na) and graphene strain ranging from weak to moderately strong. We show that the van der Waals potential can be significantly enhanced by strain, and present applications of our results to the problem of elastic scattering of atoms from graphene. In particular we find that quantum reflection can be significantly suppressed by strain, meaning that dissipative inelastic effects near the surface become of increased importance. Furthermore we introduce a method to independently estimate the Lennard-Jones parameters used in an effective model of He interacting with graphene, and determine how they depend on strain. At short distances, we find that strain tends to reduce the interaction strength by pushing the location of the adsorption potential minima to higher distances above the deformed graphene sheet. This opens up the exciting possibility of mechanically engineering an adsorption potential, with implications for the formation and observation of anisotropic low dimensional superfluid phases.