2,501 research outputs found
Gate-controllable spin-battery
We propose a gate-controllable spin-battery for spin current. The
spin-battery consists of a lateral double quantum dot under a uniform magnetic
field. A finite DC spin-current is driven out of the device by controlling a
set of gate voltages. Spin-current can also be delivered in the absence of
charge-current. The proposed device should be realizable using present
technology at low temperature.Comment: 3 pages, 3 figures, accepted by Appl. Phys. Let
Disorder-induced enhancement of transport through graphene p-n junctions
We investigate the electron transport through a graphene p-n junction under a
perpendicular magnetic field. By using Landauar-Buttiker formalism combining
with the non-equilibrium Green function method, the conductance is studied for
the clean and disordered samples. For the clean p-n junction, the conductance
is quite small. In the presence of disorders, it is strongly enhanced and
exhibits plateau structure at suitable range of disorders. Our numerical
results show that the lowest plateau can survive for a very broad range of
disorder strength, but the existence of high plateaus depends on system
parameters and sometimes can not be formed at all. When the disorder is
slightly outside of this disorder range, some conductance plateaus can still
emerge with its value lower than the ideal value. These results are in
excellent agreement with the recent experiment.Comment: 5 pages, 5 figures, submit to PRL on May 20, 200
Vibrational spectroscopy at electrolyte/electrode interfaces with graphene gratings.
Microscopic understanding of physical and electrochemical processes at electrolyte/electrode interfaces is critical for applications ranging from batteries, fuel cells to electrocatalysis. However, probing such buried interfacial processes is experimentally challenging. Infrared spectroscopy is sensitive to molecule vibrational signatures, yet to approach the interface three stringent requirements have to be met: interface specificity, sub-monolayer molecular detection sensitivity, and electrochemically stable and infrared transparent electrodes. Here we show that transparent graphene gratings electrode provide an attractive platform for vibrational spectroscopy at the electrolyte/electrode interfaces: infrared diffraction from graphene gratings offers enhanced detection sensitivity and interface specificity. We demonstrate the vibrational spectroscopy of methylene group of adsorbed sub-monolayer cetrimonium bromide molecules and reveal a reversible field-induced electrochemical deposition of cetrimonium bromide on the electrode controlled by the bias voltage. Such vibrational spectroscopy with graphene gratings is promising for real time and in situ monitoring of different chemical species at the electrolyte/electrode interfaces
Origin of Interfacial Polar Order in Incipient Ferroelectrics
There are ample experimental evidences indicating that the ferroelastic domain walls of incipient ferroelectrics, such as SrTiO3 and CaTiO3, are polar. The emergence of such interfacial polar order at a domain wall is exciting and believed to arise from the coupling between a primary order parameter, such as a strain or an antiferrodistortive (AFD) order parameter, and polarization. There have been several mechanisms proposed to explain the emergence of interfacial polar order, including biquadratic coupling, AFD-antiferroelectric coupling, and flexoelectric coupling. Using CaTiO3 as an example, we demonstrate, using both asymptotic analytics and numerical calculation, that the flexoelectric coupling is likely the dominant mechanism leading to the interfacial polar order
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