Showing papers by "Kostya S. Novoselov published in 2005"
TL;DR: This study reports an experimental study of a condensed-matter system (graphene, a single atomic layer of carbon) in which electron transport is essentially governed by Dirac's (relativistic) equation and reveals a variety of unusual phenomena that are characteristic of two-dimensional Dirac fermions.
Abstract: Quantum electrodynamics (resulting from the merger of quantum mechanics and relativity theory) has provided a clear understanding of phenomena ranging from particle physics to cosmology and from astrophysics to quantum chemistry. The ideas underlying quantum electrodynamics also influence the theory of condensed matter, but quantum relativistic effects are usually minute in the known experimental systems that can be described accurately by the non-relativistic Schrodinger equation. Here we report an experimental study of a condensed-matter system (graphene, a single atomic layer of carbon) in which electron transport is essentially governed by Dirac's (relativistic) equation. The charge carriers in graphene mimic relativistic particles with zero rest mass and have an effective 'speed of light' c* approximately 10(6) m s(-1). Our study reveals a variety of unusual phenomena that are characteristic of two-dimensional Dirac fermions. In particular we have observed the following: first, graphene's conductivity never falls below a minimum value corresponding to the quantum unit of conductance, even when concentrations of charge carriers tend to zero; second, the integer quantum Hall effect in graphene is anomalous in that it occurs at half-integer filling factors; and third, the cyclotron mass m(c) of massless carriers in graphene is described by E = m(c)c*2. This two-dimensional system is not only interesting in itself but also allows access to the subtle and rich physics of quantum electrodynamics in a bench-top experiment.
18,958 citations
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: In this paper, a magnetic tunnel junction having spin filtering by a magnetic barrier was investigated, where a relatively strong external field rotates magnetizations of both ferromagnetic electrodes in the tunnel junction with the magnetic barrier simultaneously so that the two are always parallel to each other.
Abstract: This letter deals with a magnetic tunnel junction having spin filtering by a magnetic barrier. We performed experiments in which a relatively strong external field rotates magnetizations of both ferromagnetic electrodes in the tunnel junction with the magnetic barrier simultaneously so that the two are always parallel to each other. The tunnel magnetoresistance induced in this way was over 16% at 300K. The angular dependency of the tunnel current on the layer magnetizations indicates that the barrier contains antiferromagnetic oxide. To achieve the described effect the magnetic electrode of the junction was oxidized prior to forming the Al2O3 layer.
10 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.