1,017 research outputs found
Tunable Negative Differential Resistance controlled by Spin Blockade in Single Electron Transistors
We demonstrate a tunable negative differential resistance controlled by spin
blockade in single electron transistors. The single electron transistors
containing a few electrons and spin polarized source and drain contacts were
formed in GaAs/GaAlAs heterojunctions using metallic gates. Coulomb blockade
measurements performed as a function of applied source-drain bias, electron
number and magnetic field reveal well defined regimes where a decrease in the
current is observed with increasing bias. We establish that the origin of the
negative differential regime is the spin-polarized detection of electrons
combined with a long spin relaxation time in the dot. These results indicate
new functionalities that may be utilized in nano-spintronic devices in which
the spin state is electro-statically controlled via the electron occupation
number.Comment: 8 pages, 4 figure
Spatial interference from well-separated condensates
We use magnetic levitation and a variable-separation dual optical plug to
obtain clear spatial interference between two condensates axially separated by
up to 0.25 mm -- the largest separation observed with this kind of
interferometer. Clear planar fringes are observed using standard (i.e.
non-tomographic) resonant absorption imaging. The effect of a weak inverted
parabola potential on fringe separation is observed and agrees well with
theory.Comment: 4 pages, 5 figures - modified to take into account referees'
improvement
Spin splitting in open quantum dots
We present results from a theoretical and experimental study of
spin-splitting in small open lateral quantum dots (i.e. in the regime when the
dot is connected to the reservoirs via leads that support one or more
propagating modes). We demonstrate that the magnetoconductance shows a
pronounced splitting of the conductance peaks (or dips) which persists over a
wide range of magnetic fields (from zero field to the edge-state regime) and is
virtually independent of magnetic field. A numerical analysis of the
conductance and the dot eigenspectrum indicates that this feature is related to
a lifting of the spin degeneracy in the corresponding closed dot associated
with the interaction between electrons of opposite spin.Comment: 4 pages, 4 figures 1 misdirected figure reference corrected mismatch
between spin-up/spin-down notation in figure 3-4 and discussion corrected,
clarifications in text adde
Coherent Transport Through a Quadruple Point in a Few Electron Triple Dot
A few electron double electrostatic lateral quantum dot can be transformed
into a few electron triple quantum dot by applying a different combination of
gate voltages. Quadruple points have been achieved at which all three dots are
simultaneously on resonance. At these special points in the stability diagram
four occupation configurations are possible. Both charge detection and
transport experiments have been performed on this device. In this short paper
we present data and confirm that transport is coherent by observing a Pi phase
shift in magneto-conductance oscillations as one passes through the quadruple
point.Comment: To be published in ICPS Conf. Proceedings 200
The Addition Spectrum of a Lateral Dot from Coulomb and Spin Blockade Spectroscopy
Transport measurements are presented on a class of electrostatically defined
lateral dots within a high mobility two dimensional electron gas (2DEG). The
new design allows Coulomb Blockade(CB) measurements to be performed on a single
lateral dot containing 0, 1 to over 50 electrons. The CB measurements are
enhanced by the spin polarized injection from and into 2DEG magnetic edge
states. This combines the measurement of charge with the measurement of spin
through spin blockade spectroscopy. The results of Coulomb and spin blockade
spectroscopy for first 45 electrons enable us to construct the addition
spectrum of a lateral device. We also demonstrate that a lateral dot containing
a single electron is an effective local probe of a 2DEG edge.Comment: 4 pages, 4 figures submitted to Physical Review
A Tuneable Few Electron Triple Quantum Dot
In this paper we report on a tuneable few electron lateral triple quantum dot
design. The quantum dot potentials are arranged in series. The device is aimed
at studies of triple quantum dot properties where knowing the exact number of
electrons is important as well as quantum information applications involving
electron spin qubits. We demonstrate tuning strategies for achieving required
resonant conditions such as quadruple points where all three quantum dots are
on resonance. We find that in such a device resonant conditions at specific
configurations are accompanied by novel charge transfer behaviour.Comment: 11 pages, 4 figure
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