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 $GaAs$ 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