569 research outputs found
Spin transport through a single self-assembled InAs quantum dot with ferromagnetic leads
We have fabricated a lateral double barrier magnetic tunnel junction (MTJ)
which consists of a single self-assembled InAs quantum dot (QD) with
ferromagnetic Co leads. The MTJ shows clear hysteretic tunnel magnetoresistance
(TMR) effect, which is evidence for spin transport through a single
semiconductor QD. The TMR ratio and the curve shapes are varied by changing the
gate voltage.Comment: 4 pages, 3 figure
Coherent Manipulation of Individual Electron Spin in a Double Quantum Dot Integrated with a Micro-Magnet
We report the coherent manipulation of electron spins in a double quantum dot
integrated with a micro-magnet. We performed electric dipole spin resonance
experiments in the continuous wave (CW) and pump-and-probe modes. We observed
two resonant CW peaks and two Rabi oscillations of the quantum dot current by
sweeping an external magnetic field at a fixed frequency. Two peaks and
oscillations are measured at different resonant magnetic field, which reflects
the fact that the local magnetic fields at each quantum dot are modulated by
the stray field of a micro-magnet. As predicted with a density matrix approach,
the CW current is quadratic with respect to microwave (MW) voltage while the
Rabi frequency (\nu_Rabi) is linear. The difference between the \nu_Rabi values
of two Rabi oscillations directly reflects the MW electric field across the two
dots. These results show that the spins on each dot can be manipulated
coherently at will by tuning the micro-magnet alignment and MW electric field.Comment: 5 pages, 3 figure
Novel ordering of an S = 1/2 quasi one-dimensional Ising-like anitiferromagnet in magnetic field
High-field specific heat measurements on BaCo2V2O8, which is a good
realization of an S = 1/2 quasi one-dimensional Ising-like antifferomagnet,
have been performed in magnetic fields up to 12 T along the chain and at
temperature down to 200 mK. We have found a new magnetic ordered state in the
field-induced phase above Hc ~ 3.9 T. We suggest that a novel type of the
incommensurate order, which has no correspondence to the classical spin system,
is realized in the field-induced phase.Comment: 4pages, 4figure
Longitudinal SDW order in a quasi-1D Ising-like quantum antiferromagnet
From neutron diffraction measurements on a quasi-1D Ising-like Co
spin compound BaCoVO, we observed an appearance
of a novel type of incommensurate ordering in magnetic fields. This ordering is
essentially different from the N{\' e}el-type ordering, which is expected for
the classical system, and is caused by quantum fluctuation inherent in the
quantum spin chain. A Tomonaga-Luttinger liquid (TLL) nature characteristic of
the gapless quantum 1D system is responsible for the realization of the
incommensurate ordering.Comment: 4pages, 4figur
Development of a new, fully automated system for electron backscatter diffraction (EBSD)-based large volume three-dimensional microstructure mapping using serial sectioning by mechanical polishing, and its application to the analysis of special boundaries in 316L stainless steel
Two-qubit Gate of Combined Single Spin Rotation and Inter-dot Spin Exchange in a Double Quantum Dot
A crucial requirement for quantum information processing is the realization
of multiple-qubit quantum gates. Here, we demonstrate an electron spin based
all-electrical two-qubit gate consisting of single spin rotations and inter-dot
spin exchange in a double quantum dot. A partially entangled output state is
obtained by the application of the two-qubit gate to an initial, uncorrelated
state. We find that the degree of entanglement is controllable by the exchange
operation time. The approach represents a key step towards the realization of
universal multiple qubit gates.Comment: accepted for publication, in press Phys.Rev.Lett. 201
Complementary use of TEM and APT for the investigation of steels nanostructured by severe plastic deformation
The properties of bulk nanostructured materials are often controlled by
atomic scale features like segregation along defects or composition gradients.
Here we discuss about the complimentary use of TEM and APT to obtain a full
description of nanostructures. The advantages and limitations of both
techniques are highlighted on the basis of experimental data collected in
severely deformed steels with a special emphasis on carbon spatial
distribution
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