66 research outputs found
A magnetic barrier in confined two-dimensional electron gases: Nanomagnetometers and magnetic switches
We investigate the conductance properties of a hybrid
ferromagnet-semiconductor structure consisting of a confined two-dimensional
electron gas and a transverse ferromagnetic strip on top. Within the framework
of the Landauer-B\"uttiker model, we develop an alternative way to consider
magnetic fields. Our method describes devices ranging from a recently realized
nanomagnetometer down to quasi one-dimensional quantum wires. We provide a
rigorous way to relate the measured resistance to the actual magnetization of
the strip. Regarding the quasi one-dimensional wires we propose a new device
application, a tunable magnetic switch.Comment: 4 pages, 5 figures included, to be published in Applied Physics
Letter
Adiabatic charge and spin pumping through quantum dots with ferromagnetic leads
We study adiabatic pumping of electrons through quantum dots attached to
ferromagnetic leads. Hereby we make use of a real-time diagrammatic technique
in the adiabatic limit that takes into account strong Coulomb interaction in
the dot. We analyze the degree of spin polarization of electrons pumped from a
ferromagnet through the dot to a nonmagnetic lead (N-dot-F) as well as the
dependence of the pumped charge on the relative leads' magnetization
orientations for a spin-valve (F-dot-F) structure. For the former case, we find
that, depending on the relative coupling strength to the leads, spin and charge
can, on average, be pumped in opposite directions. For the latter case, we find
an angular dependence of the pumped charge, that becomes more and more
anharmonic for large spin polarization in the leads.Comment: 9 pages, 7 figures, published in Phys. Rev.
Generation of pure spin currents by superconducting proximity effect in quantum dots
We investigate electronic transport in a three-terminal hybrid system,
composed by an interacting quantum dot tunnel coupled to one superconducting,
one ferromagnetic, and one normal lead. Despite the tendency of the charging
energy to suppress the superconducting proximity effect when the quantum dot is
in equilibrium, the non-equilibrium proximity effect can give rise to a large
Andreev current. The presence of the ferromagnet can lead to a finite spin
accumulation on the dot. We find that the interplay of the Andreev current and
spin accumulation can generate a pure spin current, with no associated charge
transport, in the normal lead. This situation is realised by tuning the
quantum-dot spectrum by means of a gate voltage.Comment: 6 pages, 5 figure
Signatures of spin-related phases in transport through regular polygons
We address the subject of transport in one-dimensional ballistic polygon
loops subject to Rashba spin-orbit coupling. We identify the role played by the
polygon vertices in the accumulation of spin-related phases by studying
interference effects as a function of the spin-orbit coupling strength. We find
that the vertices act as strong spin-scattering centers that hinder the
developing of Aharovov-Casher and Berry phases. In particular, we show that the
oscillation frequency of interference pattern can be doubled by modifying the
shape of the loop from a square to a circle.Comment: 4 pages, 4 figures. To appear in Phys. Rev.
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