1,721,299 research outputs found
Quantum Rings in Magnetic Field and Spin Current Generation
No full textWe propose three different mechanisms for pumping spin-polarized currents in a ballistic circuit
using a time-dependent magnetic field acting on an asymmetrically connected quantum ring at half
filling. The first mechanism works thanks to a rotating magnetic field and produces an alternating
current with a partial spin polarization. The second mechanism works by rotating the ring in a
constant field; like the former case, it produces an alternating charge current but the spin current
is d.c.; both methods do not require a spin-orbit interaction to achieve the polarized current, but
the rotating ring could be used to measure the spin-orbit interaction in the ring using characteristic
oscillations. On the other hand, the last mechanism that we propose depends on the spin-orbit
interaction in an essential way, and requires a time-dependent magnetic field in the plane of the
ring. This arrangement can be designed to pump a purely spin current. The absence of a charge
current is demonstrated analytically. Moreover, a simple formula for the current is derived and
compared to the numerical results
Interacting electrons in one dimensional quantum rings in a threading magnetic field: Spin phases and correlations
No full text
Pumping through a Luttinger liquid ring threaded by a time-varying magnetic field
Full text linkWe consider a quantum ring laterally connected to open one-dimensional leads described within the Luttinger
liquid (LL) model and subject to a time-dependent driving magnetic field ö(t ). The closed loop is obtained by
connecting two points of the LL by a weak link, which is treated exactly to lowest order in perturbation theory.
Analytical results for the current across the weak link, as well as in the external circuit and inside the loop, are
obtained. We pay special attention to the case of smooth magnetic pulses such that the response of the system is
approximately adiabatic. We find that the response to the flux ö is linear only if ö is a small fraction of a flux
quantum ö0. By inserting whole quanta, a current goes in the external wires as two bunches, separated by a time
proportional to the length of the loop, and a net pumped current in the external wires is produced. This kind of
pumping is consistent with the predictions of the corresponding tight-binding model in the uncorrelated limit,
but is not destroyed by electron-electron interactions
The 1974 Ethiopian Revolution at 40: Social, Economic, and Political Legacies
No full textColonial and Global Histor
Magnetzation transfer by a quantum ring device
No full textWe show that a tight-binding model device consisting of a laterally connected ring at half filling
in a tangent time-dependent magnetic field can in principle be designed to pump a purely spin current.
The process exploits the spin-orbit interaction in the ring. This behavior is understood analytically and
found to be robust with respect to temperature and small deviations from half fillin
Wage labour and capitalism: a comparative and historical analysis of Eritrea and Kenya
No full textColonial and Global Histor
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