1,687 research outputs found
Electronic transport through nuclear-spin-polarization-induced quantum wire
Electron transport in a new low-dimensional structure - the nuclear spin
polarization induced quantum wire (NSPI QW) is theoretically studied. In the
proposed system the local nuclear spin polarization creates the effective
hyperfine field which confines the electrons with the spins opposite to the
hyperfine field to the regions of maximal nuclear spin polarization. The
influence of the nuclear spin relaxation and diffusion on the electron energy
spectrum and on the conductance of the quantum wire is calculated and the
experimental feasibility is discussed.Comment: 5 pages, 4 figure
Quantum information processing based on P-31 nuclear spin qubits in a quasi-one-dimensional Si-28 nanowire
We suggest a new method of quantum information processing based on the
precise placing of P-31 isotope atoms in a quasi-one-dimensional Si-28 nanowire
using isotope engineering and neutron-transmutation doping of the grown
structures. In our structure, interqubit entanglement is based on the indirect
interaction of P-31 nuclear spins with electrons localized in a nanowire. This
allows one to control the coupling between distant qubits and between qubits
separated by non-qubit neighboring nodes. The suggested method enables one to
fabricate structures using present-day nanolithography. Numerical estimates
show the feasibility of the proposed device and method of operation.Comment: 7 pages, 4 figure
Massive Spin Collective Mode in Quantum Hall Ferromagnet
It is shown that the collective spin rotation of a single Skyrmion in quantum
Hall ferromagnet can be regarded as precession of the entire spin texture in
the external magnetic field, with an effective moment of inertia which becomes
infinite in the zero g-factor limit. This low-lying spin excitation may
dramatically enhance the nuclear spin relaxation rate via the hyperfine
interaction in the quantum well slightly away from filling factor equal one.Comment: 4 page
Nucleus-mediated spin-flip transitions in GaAs quantum dots
Spin-flip rates in GaAs quantum dots can be quite slow, thus opening up the
possibilities to manipulate spin states in the dots. We present here
estimations of inelastic spin-flip rates mediated by hyperfine interaction with
nuclei. Under general assumptions the nucleus mediated rate is proportional to
the phonon relaxation rate for the corresponding non-spin-flip transitions. The
rate can be accelerated in the vicinity of a singlet-triplet excited states
crossing. The small proportionality coefficient depends inversely on the number
of nuclei in the quantum dot. We compare our results with known mechanisms of
spin-flip in quantum dot.Comment: RevTex 4 pages, 1 figure, submitted to Phys. Rev.
Hohenbuehelia (Pleurotaceae) in western Paraná, Brazil
Hohenbuehelia (Pleurotaceae) in western Paraná, Brazil </htm
Is the magnetic field necessary for the Aharonov-Bohm effect in mesoscopics?
A new class of topological mesoscopic phenomena in absence of external
magnetic field (meso-nucleo-spinics)is predicted, which is based on combined
action of the nonequilibrium nuclear spin population and charge carriers
spin-orbit interaction . As an example, we show that Aharonov-Bohm like
oscillations of the persistent current in GaAs/AlGaAs based mesoscopic rings
may exist, in the absence of the external magnetic field, provided that a
topologically nontrivial strongly nonequilibrium nuclear spin population is
created. This phenomenon is due to the breaking, via the spin-orbit coupling,
of the clock wise - anti clock wise symmetry of the charge carriers momentum,
which results in the oscillatory in time persistent current.Comment: 14 pages, Late
Bac-pool Sequencing And Assembly Of 19 Mb Of The Complex Sugarcane Genome
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Sequencing plant genomes are often challenging because of their complex architecture and high content of repetitive sequences. Sugarcane has one of the most complex genomes. It is highly polyploid, preserves intact homeologous chromosomes from its parental species and contains 55% repetitive sequences. Although bacterial artificial chromosome (BAC) libraries have emerged as an alternative for accessing the sugarcane genome, sequencing individual clones is laborious and expensive. Here, we present a strategy for sequencing and assembly reads produced from the DNA of pooled BAC clones. A set of 178 BAC clones, randomly sampled from the SP80-3280 sugarcane BAC library, was pooled and sequenced using the Illumina HiSeq2000 and PacBio platforms. A hybrid assembly strategy was used to generate 2,451 scaffolds comprising 19.2 MB of assembled genome sequence. Scaffolds of >= 20 Kb corresponded to 80% of the assembled sequences, and the full sequences of forty BACs were recovered in one or two contigs. Alignment of the BAC scaffolds with the chromosome sequences of sorghum showed a high degree of collinearity and gene order. The alignment of the BAC scaffolds to the 10 sorghum chromosomes suggests that the genome of the SP80-3280 sugarcane variety is similar to 19% contracted in relation to the sorghum genome. In conclusion, our data show that sequencing pools composed of high numbers of BAC clones may help to construct a reference scaffold map of the sugarcane genome.7[FAPESP - 10/50114-4]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP
Nuclear Spin Qubit Dephasing Time in the Integer Quantum Hall Effect Regime
We report the first theoretical estimate of the nuclear-spin dephasing time
T_2 owing to the spin interaction with the two-dimensional electron gas, when
the latter is in the integer quantum Hall state, in a two-dimensional
heterojunction or quantum well at low temperature and in large applied magnetic
field. We establish that the leading mechanism of dephasing is due to the
impurity potentials that influence the dynamics of the spin via virtual
magnetic spin-exciton scattering. Implications of our results for
implementation of nuclear spins as quantum bits (qubits) for quantum computing
are discussed.Comment: 19 pages in plain Te
Combined effect of Zeeman splitting and spin-orbit interaction on the Josephson current in a S-2DEG-S structure
We analyze new spin effects in current-carrying state of superconductor-2D
electron gas-superconductor (S-2DEG-S) device with spin-polarized nuclei in
2DEG region. The hyperfine interaction of 2D electrons with nuclear spins,
described by the effective magnetic field B, produces Zeeman splitting of
Andreev levels without orbital effects, that leads to the interference pattern
of supercurrent oscillations over B. The spin-orbit effects in 2DEG cause
strongly anisotropic dependence of the Josephson current on the direction of B,
which may be used as a probe for the spin-orbit interaction intensity. Under
certain conditions, the system reveals the properties of pi-junction.Comment: 4 pages, 4 figure
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