Showing papers by "Kostya S. Novoselov published in 2006"
TL;DR: In this paper, a third type of integer quantum Hall effect is reported in bilayer graphene, where charge carriers have a parabolic energy spectrum but are chiral and show Berry's phase 2π affecting their quantum dynamics.
Abstract: There are two known distinct types of the integer quantum Hall effect. One is the conventional quantum Hall effect, characteristic of two-dimensional semiconductor systems1,2, and the other is its relativistic counterpart observed in graphene, where charge carriers mimic Dirac fermions characterized by Berry’s phase π, which results in shifted positions of the Hall plateaus3,4,5,6,7,8,9. Here we report a third type of the integer quantum Hall effect. Charge carriers in bilayer graphene have a parabolic energy spectrum but are chiral and show Berry’s phase 2π affecting their quantum dynamics. The Landau quantization of these fermions results in plateaus in Hall conductivity at standard integer positions, but the last (zero-level) plateau is missing. The zero-level anomaly is accompanied by metallic conductivity in the limit of low concentrations and high magnetic fields, in stark contrast to the conventional, insulating behaviour in this regime. The revealed chiral fermions have no known analogues and present an intriguing case for quantum-mechanical studies.
1,665 citations
TL;DR: Graphene weak-localization magnetoresistance is strongly suppressed and, in some cases, completely absent, due to mesoscopic corrugations of graphene sheets which can cause a dephasing effect similar to that of a random magnetic field.
Abstract: Low-field magnetoresistance is ubiquitous in low-dimensional metallic systems with high resistivity and well understood as arising due to quantum interference on self-intersecting diffusive trajectories. We have found that in graphene this weak-localization magnetoresistance is strongly suppressed and, in some cases, completely absent. The unexpected observation is attributed to mesoscopic corrugations of graphene sheets which can cause a dephasing effect similar to that of a random magnetic field.
783 citations
TL;DR: In this paper, soft magnetic NiFe electrodes have been used to inject polarized spins into graphene, and a 10% change in resistance has been observed as the electrodes switch from the parallel to the antiparallel state.
Abstract: Graphene-a single atomic layer of graphite-is a recently found two-dimensional (2-D) form of carbon, which exhibits high crystal quality and ballistic electron transport at room temperature. Soft magnetic NiFe electrodes have been used to inject polarized spins into graphene, and a 10% change in resistance has been observed as the electrodes switch from the parallel to the antiparallel state. This coupled with the fact that a field-effect electrode can modulate the conductivity of these graphene films makes them exciting potential candidates for spin electronic devices
368 citations
TL;DR: In this article, the authors describe probes of a local electric field, which are capable of detecting an electric charge as small as the charge of one electron e, operational under ambient conditions and having a spatial resolution down to 100nm.
Abstract: We describe probes of a local electric field, which are capable of detecting an electric charge as small as the charge of one electron e, operational under ambient conditions and having a spatial resolution down to 100nm. The submicron-sized probes were made from a high-density high-mobility two-dimensional electron gas, which is sensitive to the presence of electric charges near its surface. We demonstrate the possibility of using such microprobes for life-science applications by measuring an electric response of individual yeast cells to abrupt changes in their environment.
79 citations
TL;DR: In this article, the movement of a micron-size section of an individual domain wall in a uniaxial garnet film was studied using ballistic Hall micromagnetometry.
Abstract: The movement of a micron-size section of an individual domain wall in a uniaxial garnet film was studied using ballistic Hall micromagnetometry. The wall propagated in characteristic Barkhausen jumps, with the distribution in jump size $S$, following the power-law relation, $D(S)\ensuremath{\propto}{S}^{\ensuremath{-}\ensuremath{\tau}}$. In addition to reporting on the suitability of employing this alternative technique, we discuss the measurements taken of the scaling exponent $\ensuremath{\tau}$, for a single domain wall in a two-dimensional sample with magnetization perpendicular to the surface, and low pinning center concentration. This exponent was found to be $1.14\ifmmode\pm\else\textpm\fi{}0.05$ at both liquid helium and liquid nitrogen temperatures.
18 citations
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TL;DR: In this paper, a room temperature tunneling anisotropic magnetoresistance in Co/Al 2O3/NiFe junctions containing magnetic electrodes oxidized prior to forming the Al2O3 layer was reported.
Abstract: We report a room temperature tunneling anisotropic magnetoresistance in Co/Al2O3/NiFe junctions containing magnetic electrodes oxidized prior to forming the Al2O3 layer A significant change in a tunnel magnetoresistance is observed when the layer magnetizations are rotated collinearly in the junction plane by an applied external field The angular dependence of the tunneling anisotropic magnetoresistance could be explained by the presence of an antiferromagnetic oxide layer formed within the barrier
1 citations