489 research outputs found
Universal Scaling in Non-equilibrium Transport Through a Single-Channel Kondo Dot
Scaling laws and universality play an important role in our understanding of
critical phenomena and the Kondo effect. Here we present measurements of
non-equilibrium transport through a single-channel Kondo quantum dot at low
temperature and bias. We find that the low-energy Kondo conductance is
consistent with universality between temperature and bias and characterized by
a quadratic scaling exponent, as expected for the spin-1/2 Kondo effect. The
non-equilibrium Kondo transport measurements are well-described by a universal
scaling function with two scaling parameters.Comment: v2: improved introduction and theory-experiment comparsio
Experimental Realization of a Quantum Spin Pump
We demonstrate the operation of a quantum spin pump based on cyclic
radio-frequency excitation of a GaAs quantum dot, including the ability to pump
pure spin without pumping charge. The device takes advantage of bidirectional
mesoscopic fluctuations of pumped current, made spin-dependent by the
application of an in-plane Zeeman field. Spin currents are measured by placing
the pump in a focusing geometry with a spin-selective collector.Comment: related papers available at http://marcuslab.harvard.ed
Detecting Spin-Polarized Currents in Ballistic Nanostructures
We demonstrate a mesoscopic spin polarizer/analyzer system that allows the
spin polarization of current from a quantum point contact in an in-plane
magnetic field to be measured. A transverse focusing geometry is used to couple
current from an emitter point contact into a collector point contact. At large
in-plane fields, with the point contacts biased to transmit only a single spin
(g < e^2/h), the voltage across the collector depends on the spin polarization
of the current incident on it. Spin polarizations of greater than 80% are found
for both emitter and collector at 300mK and 7T in-plane field.Comment: related papers at http://marcuslab.harvard.ed
Zeeman energy and anomalous spin splitting in lateral GaAs quantum dots
The level splittings induced by a horizontal magnetic field in a parabolic
two-dimensional quantum dot with spin-orbit interaction are obtained.
Characteristic features induced by the spin-orbit coupling are the appearance
of zero-field gaps as well as energy splittings that depend on the electronic
state and the orientation of the magnetic field in the quantum-dot plane. It is
suggested that these quantum-dot properties could be used to determine the
Rashba and Dresselhaus spin-orbit intensitiesComment: 6 pages, 6 figures. To be published in Eur. Phys. J. B (2004
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