Showing papers by "Andre K. Geim published in 2005"
TL;DR: By using micromechanical cleavage, a variety of 2D crystals including single layers of boron nitride, graphite, several dichalcogenides, and complex oxides are prepared and studied.
Abstract: We report free-standing atomic crystals that are strictly 2D and can be viewed as individual atomic planes pulled out of bulk crystals or as unrolled single-wall nanotubes. By using micromechanical cleavage, we have prepared and studied a variety of 2D crystals including single layers of boron nitride, graphite, several dichalcogenides, and complex oxides. These atomically thin sheets (essentially gigantic 2D molecules unprotected from the immediate environment) are stable under ambient conditions, exhibit high crystal quality, and are continuous on a macroscopic scale.
10,586 citations
TL;DR: A nanofabricated medium consisting of electromagnetically coupled pairs of gold dots with geometry carefully designed at a 10-nm level exhibits a strong magnetic response at visible-light frequencies, including a band with negative µ.
Abstract: A great deal of attention has recently been focused on a new class of smart materials-so-called left-handed media-that exhibit highly unusual electromagnetic properties and promise new device applications. Left-handed materials require negative permeability ν, an extreme condition that has so far been achieved only for frequencies in the microwave to terahertz range. Extension of the approach described in ref. 7 to achieve the necessary high-frequency magnetic response in visible optics presents a formidable challenge, as no material-natural or artificial-is known to exhibit any magnetism at these frequencies. Here we report a nanofabricated medium consisting of electromagnetically coupled pairs of gold dots with geometry carefully designed at a 10-nm level. The medium exhibits a strong magnetic response at visible-light frequencies, including a band with negative ν. The magnetism arises owing to the excitation of an antisymmetric plasmon resonance. The high-frequency permeability qualitatively reveals itself via optical impedance matching. Our results demonstrate the feasibility of engineering magnetism at visible frequencies and pave the way towards magnetic and left-handed components for visible optics. © 2005 Nature Publishing Group.
569 citations
TL;DR: In this paper, a non-local response in Hall-shaped superconductors is studied using the time-dependent Ginzburg-Landau equations, which is a consequence of the long range correlations in a one-dimensional vortex lattice squeezed in a narrow channel by screening currents.
Abstract: Nonlocal response in Hall-shaped superconductors is studied using the time-dependent Ginzburg-Landau equations. Applying current in one pair of contacts leads to a voltage drop in another pair of contacts situated at a distance much larger than the coherence length. This effect is a consequence of the long range correlations in a one-dimensional vortex lattice squeezed in a narrow channel by screening currents. The discrete change in the number of vortices in the channel with applied magnetic field leads to a nonlocal response which is a nonmonotonous function of the magnetic field. For specific configurations of the Hall-shaped superconductor we found a rectifying effect.
12 citations
TL;DR: In this paper, the movement of individual domain walls in a ferromagnetic garnet was studied with angstrom resolution and it was shown that domain walls can be locked between adjacent crystallographic planes and propagate by distinct steps matching the lattice periodicity.
Abstract: Movements of individual domain walls in a ferromagnetic garnet were studied with angstrom resolution. The measurements reveal that domain walls can be locked between adjacent crystallographic planes and propagate by distinct steps matching the lattice periodicity.
4 citations
01 Jan 2005
TL;DR: In this paper, the movement of individual domain walls in a ferromagnetic garnet was studied with angstrom resolution and it was shown that domain walls can be locked between adjacent crystallographic planes and propagate by distinct steps matching the lattice periodicity.
Abstract: Movements of individual domain walls in a ferromagnetic garnet were studied with angstrom resolution. The measurements reveal that domain walls can be locked between adjacent crystallographic planes and propagate by distinct steps matching the lattice periodicity.
1 citations
01 Jan 2005
TL;DR: In this article, the movement of a micrometer-size section of a single domain wall in a uniaxial garnet film was studied using a ballistic Hall micromagnetometer at 77 K and 4.2 K. The wall propagated in characteristic Barkhausen jumps, with the jump size distribution following the power-law relation.
Abstract: The movement of a micrometer-size section of a single domain wall in a uniaxial garnet film was studied using a ballistic Hall micromagnetometer at 77 K and 4.2 K. The wall propagated in characteristic Barkhausen jumps, with the jump size distribution following the power-law relation, P(S) proportional to S-tau. The scaling exponent, tau, was measured as 1.14 +/- 0.05 at both temperatures. This is the first measurement of this exponent using such a device, and the first for a single wall in a two-dimensional sample with a low concentration of pinning centres, in which the magnetization of the sample is perpendicular to the surface.